staging: speakup: support more than ttyS*

The function converts strings like ttyS0 and ttyUSB0 to dev_t like (4, 64) and (188, 0). It does this by scanning tty_drivers list for corresponding device name and index. If the driver is not registered, this function returns -ENODEV. It also acquires tty_mutex.

+/**
+ * tty_dev_name_to_number - return dev_t for device name

+ * @device_name: user space name of device under /dev

+ * @dev_no: pointer to dev_t that this function will populate

+ *

+ *     This function converts device names like ttyS0 or ttyUSB1 into dev_t
+ *     like (4, 64) or (188, 1). If no corresponding driver is registered then
+ *     the function returns -ENODEV.

+ *

+ * Locking: this acquires tty_mutex

+ */
+int tty_dev_name_to_number(char *dev_name, dev_t *dev_no)

+ }

drivers/tty/tty_io.c +11 -0

+                       if (index < p->num) {
+                               *dev_no = MKDEV(p->major, p->minor_start + index);
+                               mutex_unlock(&tty_mutex);
+                               return 0;
+                       }
+               }
+
+       mutex_unlock(&tty_mutex);
+       return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(tty_dev_name_to_number);

This patch adds functionality to validate and convert either a device name or 'ser' member of synth into dev_t. Subsequent patch in this set will call it to convert user-specified device into device number. For device name, this patch does some basic sanity checks on the string passed in. It currently supports ttyS*, ttyUSB* and, for selected synths, lp*.

The patch also introduces a string member variable named 'dev_name' to struct spk_synth. 'dev_name' represents the device name - ttyUSB0 etc - which needs conversion to dev_t.

Signed-off-by Okash Khawaja <[email protected]>

---
 drivers/staging/speakup/spk_priv.h  |    2 +
 drivers/staging/speakup/spk_ttyio.c |   46 ++++++++++++++++++++++++++++++++++++
 drivers/staging/speakup/spk_types.h |    1
 3 files changed, 49 insertions(+)

drivers/staging/speakup/spk_priv.h +2 -0

@@ -40,6 +40,8 @@
 
 #define KT_SPKUP 15
 #define SPK_SYNTH_TIMEOUT 100000 /* in micro-seconds */
+#define SYNTH_DEFAULT_DEV "ttyS0"
+#define SYNTH_DEFAULT_SER 0
 
 const struct old_serial_port *spk_serial_init(int index);
 void spk_stop_serial_interrupt(void);

drivers/staging/speakup/spk_ttyio.c +1 -0

+
 struct spk_ldisc_data {
        char buf;

        struct semaphore sem;

drivers/staging/speakup/spk_ttyio.c +13 -0

+
+               return -EINVAL;
+        }
+
+       *dev_no = MKDEV(4, (64 + ser));
+       return 0;
+}
+
+static int get_dev_to_use(struct spk_synth *synth, dev_t *dev_no)
+{
+       /* use ser only when dev is not specified */
+       if (strcmp(synth->dev_name, SYNTH_DEFAULT_DEV) || synth->ser == SYNTH_DEFAULT_SER) {
+               /* for /dev/lp* check if synth is supported */

drivers/staging/speakup/spk_ttyio.c +11 -0

+
+                               return -ENOTSUPP;
+                       }
+               }
+
+               return tty_dev_name_to_number(synth->dev_name, dev_no);
+       }
+
+       return ser_to_dev(synth->ser, dev_no);
+}
+

static int spk_ttyio_ldisc_open(struct tty_struct *tty)

 {
        struct spk_ldisc_data *ldisc_data;

drivers/staging/speakup/spk_types.h +0 -0

        short flags;
        short startup;

const int checkval; /* for validating a proper synth module */

This patch introduces new module parameter, dev, which takes a string representing the device that the external synth is connected to, e.g. ttyS0, ttyUSB0 etc. This is then used to communicate with the synth. That way, speakup can support more than ttyS*. As of this patch, it only supports ttyS*, ttyUSB* and selected synths for lp*. dev parameter is only available for tty-migrated synths.

Users will either use dev or ser as both serve same purpose. This patch maintains backward compatility by allowing ser to be specified. When both are specified, whichever is non-default, i.e. not ttyS0, is used. If both are non-default then dev is used.

Signed-off-by Okash Khawaja <[email protected]>

Reviewed-by Samuel Thibault <[email protected]>

---
 drivers/staging/speakup/speakup_acntsa.c |    3 +++
 drivers/staging/speakup/speakup_apollo.c |    3 +++
 drivers/staging/speakup/speakup_audptr.c |    3 +++
 drivers/staging/speakup/speakup_bns.c    |    3 +++
 drivers/staging/speakup/speakup_decext.c |    3 +++
 drivers/staging/speakup/speakup_dectlk.c |    3 +++
 drivers/staging/speakup/speakup_dummy.c  |    3 +++
 drivers/staging/speakup/speakup_ltlk.c   |    3 +++
 drivers/staging/speakup/speakup_spkout.c |    3 +++
 drivers/staging/speakup/speakup_txprt.c  |    3 +++
 drivers/staging/speakup/spk_ttyio.c      |   15 +++++++--------
 11 files changed, 37 insertions(+), 8 deletions(-)

drivers/staging/speakup/speakup_acntsa.c +3 -0

@@ -96,6 +96,7 @@ static struct spk_synth synth_acntsa = {
        .trigger = 50,
        .jiffies = 30,
        .full = 40000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -135,9 +136,11 @@ static int synth_probe(struct spk_synth
 }
 
 module_param_named(ser, synth_acntsa.ser, int, 0444);
+module_param_named(dev, synth_acntsa.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_acntsa.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_acntsa);

drivers/staging/speakup/speakup_apollo.c +3 -0

@@ -105,6 +105,7 @@ static struct spk_synth synth_apollo = {
        .trigger = 50,
        .jiffies = 50,
        .full = 40000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -199,9 +200,11 @@ static void do_catch_up(struct spk_synth
 }
 
 module_param_named(ser, synth_apollo.ser, int, 0444);
+module_param_named(dev, synth_apollo.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_apollo.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_apollo);

drivers/staging/speakup/speakup_audptr.c +3 -0

@@ -100,6 +100,7 @@ static struct spk_synth synth_audptr = {
        .trigger = 50,
        .jiffies = 30,
        .full = 18000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -162,9 +163,11 @@ static int synth_probe(struct spk_synth
 }
 
 module_param_named(ser, synth_audptr.ser, int, 0444);
+module_param_named(dev, synth_audptr.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_audptr.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_audptr);

drivers/staging/speakup/speakup_bns.c +3 -0

@@ -93,6 +93,7 @@ static struct spk_synth synth_bns = {
        .trigger = 50,
        .jiffies = 50,
        .full = 40000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -119,9 +120,11 @@ static struct spk_synth synth_bns = {
 };
 
 module_param_named(ser, synth_bns.ser, int, 0444);
+module_param_named(dev, synth_bns.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_bns.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_bns);

drivers/staging/speakup/speakup_decext.c +3 -0

@@ -120,6 +120,7 @@ static struct spk_synth synth_decext = {
        .jiffies = 50,
        .full = 40000,
        .flags = SF_DEC,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -226,9 +227,11 @@ static void synth_flush(struct spk_synth
 }
 
 module_param_named(ser, synth_decext.ser, int, 0444);
+module_param_named(dev, synth_decext.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_decext.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_decext);

drivers/staging/speakup/speakup_dectlk.c +3 -0

@@ -124,6 +124,7 @@ static struct spk_synth synth_dectlk = {
        .trigger = 50,
        .jiffies = 50,
        .full = 40000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -298,9 +299,11 @@ static void synth_flush(struct spk_synth
 }
 
 module_param_named(ser, synth_dectlk.ser, int, 0444);
+module_param_named(dev, synth_dectlk.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_dectlk.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_dectlk);

drivers/staging/speakup/speakup_dummy.c +3 -0

@@ -95,6 +95,7 @@ static struct spk_synth synth_dummy = {
        .trigger = 50,
        .jiffies = 50,
        .full = 40000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -121,9 +122,11 @@ static struct spk_synth synth_dummy = {
 };
 
 module_param_named(ser, synth_dummy.ser, int, 0444);
+module_param_named(dev, synth_dummy.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_dummy.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_dummy);

drivers/staging/speakup/speakup_ltlk.c +3 -0

@@ -107,6 +107,7 @@ static struct spk_synth synth_ltlk = {
        .trigger = 50,
        .jiffies = 50,
        .full = 40000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -166,9 +167,11 @@ static int synth_probe(struct spk_synth
 }
 
 module_param_named(ser, synth_ltlk.ser, int, 0444);
+module_param_named(dev, synth_ltlk.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_ltlk.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_ltlk);

drivers/staging/speakup/speakup_spkout.c +3 -0

@@ -98,6 +98,7 @@ static struct spk_synth synth_spkout = {
        .trigger = 50,
        .jiffies = 50,
        .full = 40000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -130,9 +131,11 @@ static void synth_flush(struct spk_synth
 }
 
 module_param_named(ser, synth_spkout.ser, int, 0444);
+module_param_named(dev, synth_spkout.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_spkout.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_spkout);

drivers/staging/speakup/speakup_txprt.c +3 -0

@@ -92,6 +92,7 @@ static struct spk_synth synth_txprt = {
        .trigger = 50,
        .jiffies = 50,
        .full = 40000,
+       .dev_name = SYNTH_DEFAULT_DEV,
        .startup = SYNTH_START,
        .checkval = SYNTH_CHECK,
        .vars = vars,

@@ -118,9 +119,11 @@ static struct spk_synth synth_txprt = {
 };
 
 module_param_named(ser, synth_txprt.ser, int, 0444);
+module_param_named(dev, synth_txprt.dev_name, charp, S_IRUGO);
 module_param_named(start, synth_txprt.startup, short, 0444);
 
 MODULE_PARM_DESC(ser, "Set the serial port for the synthesizer (0-based).");
+MODULE_PARM_DESC(dev, "Set the device e.g. ttyUSB0, for the synthesizer.");
 MODULE_PARM_DESC(start, "Start the synthesizer once it is loaded.");
 
 module_spk_synth(synth_txprt);

drivers/staging/speakup/spk_ttyio.c +7 -8

@@ -151,11 +151,12 @@ static inline void get_termios(struct tt
        up_read(&tty->termios_rwsem);
 }
 
-static int spk_ttyio_initialise_ldisc(int ser)
+static int spk_ttyio_initialise_ldisc(struct spk_synth *synth)
 {
        int ret = 0;
        struct tty_struct *tty;
        struct ktermios tmp_termios;
+       dev_t dev;
 
        ret = tty_register_ldisc(N_SPEAKUP, &spk_ttyio_ldisc_ops);
        if (ret) {

@@ -163,13 +164,11 @@ static int spk_ttyio_initialise_ldisc(in
                return ret;
        }
 
-       if (ser < 0 || ser > (255 - 64)) {
-               pr_err("speakup: Invalid ser param. Must be between 0 and 191 inclusive.\n");
-               return -EINVAL;
-       }
+       ret = get_dev_to_use(synth, &dev);
+       if (ret)
+               return ret;
 
-       /* TODO: support more than ttyS* */
-       tty = tty_open_by_driver(MKDEV(4, (ser +  64)), NULL, NULL);
+       tty = tty_open_by_driver(dev, NULL, NULL);
        if (IS_ERR(tty))
                return PTR_ERR(tty);
 

@@ -281,7 +280,7 @@ static void spk_ttyio_flush_buffer(void)
 
 int spk_ttyio_synth_probe(struct spk_synth *synth)
 {
-       int rv = spk_ttyio_initialise_ldisc(synth->ser);
+       int rv = spk_ttyio_initialise_ldisc(synth);
 
        if (rv)
                return rv;

Quoted 2 lines

+const char *lp_supported[] = { "acntsa", "bns", "dummy", "txprt" };

static ?

drivers/staging/speakup/spk_ttyio.c struct spk_ldisc_data { · line 27

Quoted 4 lines

drivers/staging/speakup/spk_ttyio.c +3 -0

+       if (ser < 0 || ser > (255 - 64)) {
 
+                pr_err("speakup: Invalid ser param. \
+                               Must be between 0 and 191 inclusive.\n");

Just make it one line.

drivers/staging/speakup/spk_ttyio.c struct spk_ldisc_data { · line 49

Quoted 7 lines

drivers/staging/speakup/spk_ttyio.c +7 -0

+
+                       for (i = 0; i < ARRAY_SIZE(lp_supported); i++) {
+                               if (strcmp(synth->name, lp_supported[i]) == 0)
+                                       break;
+                       }
+
+                       if (i >= ARRAY_SIZE(lp_supported)) {

match_string()

drivers/staging/speakup/spk_ttyio.c struct spk_ldisc_data { · line 53

Quoted 6 lines

drivers/staging/speakup/spk_ttyio.c +4 -0

+                               pr_err("speakup: lp* is only supported on:");
 
+                               for (i = 0; i < ARRAY_SIZE(lp_supported); i++)
+                                       pr_cont(" %s", lp_supported[i]);
+                               pr_cont("\n");

pr_cont() is not the best idea, though I think it will be rare cases when it might be broken in pieces.

Quoted 21 lines

drivers/staging/speakup/spk_ttyio.c +11 -0

+
+                               return -ENOTSUPP;
+                       }
+               }
+
+               return tty_dev_name_to_number(synth->dev_name, dev_no);
+       }
+
+       return ser_to_dev(synth->ser, dev_no);
+}
+
 static int spk_ttyio_ldisc_open(struct tty_struct *tty)
 {
        struct spk_ldisc_data *ldisc_data;

drivers/staging/speakup/spk_types.h +0 -0

@@ -169,6 +169,7 @@ struct spk_synth {
        int jiffies;
        int full;
        int ser;

drivers/staging/speakup/spk_types.h struct spk_synth { · line 172

Quoted 1 line

drivers/staging/speakup/spk_types.h +1 -0

+       char *dev_name;

const ?

Quoted 6 lines · Andy Shevchenko

drivers/staging/speakup/spk_ttyio.c struct spk_ldisc_data { · line 27

Quoted 4 lines

drivers/staging/speakup/spk_ttyio.c +3 -0

+       if (ser < 0 || ser > (255 - 64)) {
 
+                pr_err("speakup: Invalid ser param. \
+                               Must be between 0 and 191 inclusive.\n");

Just make it one line.

Is it okay if it becomes larger than 80 chars?

Quoted 6 lines

Quoted 5 lines

drivers/staging/speakup/spk_ttyio.c +4 -0

+                               pr_err("speakup: lp* is only supported on:");
 
+                               for (i = 0; i < ARRAY_SIZE(lp_supported); i++)
+                                       pr_cont(" %s", lp_supported[i]);
+                               pr_cont("\n");

Quoted 2 lines

pr_cont() is not the best idea, though I think it will be rare cases when it might be broken in pieces.

Hmm... I would like to keep it if it doesn't incur an overhead. It also indicates to the reader that this all part of same output line. Let me know what you think.

Quoted 7 lines

Quoted 6 lines

drivers/staging/speakup/spk_types.h +0 -0

@@ -169,6 +169,7 @@ struct spk_synth {
        int jiffies;
        int full;
        int ser;

Quoted 3 lines

drivers/staging/speakup/spk_types.h struct spk_synth { · line 172

Quoted 1 line

drivers/staging/speakup/spk_types.h +1 -0

+       char *dev_name;

const ?

This becomes the target of module_param in following patch. It complains when set to const.

Quoted 8 lines · Okash Khawaja

Quoted 5 lines · Andy Shevchenko

drivers/staging/speakup/spk_ttyio.c struct spk_ldisc_data { · line 27

Quoted 3 lines

drivers/staging/speakup/spk_ttyio.c +3 -0

+       if (ser < 0 || ser > (255 - 64)) {
+                pr_err("speakup: Invalid ser param. \
+                               Must be between 0 and 191 inclusive.\n");

Just make it one line.

Is it okay if it becomes larger than 80 chars?

Yes. Even checkpatch will not complain in this case.

This patch adds functionality to validate and convert either a device name or 'ser' member of synth into dev_t. Subsequent patch in this set will call it to convert user-specified device into device number. For device name, this patch does some basic sanity checks on the string passed in. It currently supports ttyS*, ttyUSB* and, for selected synths, lp*.

The patch also introduces a string member variable named 'dev_name' to struct spk_synth. 'dev_name' represents the device name - ttyUSB0 etc - which needs conversion to dev_t.

Signed-off-by Okash Khawaja <[email protected]>

---
 drivers/staging/speakup/spk_priv.h  |    2 +
 drivers/staging/speakup/spk_ttyio.c |   46 ++++++++++++++++++++++++++++++++++++
 drivers/staging/speakup/spk_types.h |    1 
 3 files changed, 49 insertions(+)

drivers/staging/speakup/spk_priv.h +2 -0

@@ -40,6 +40,8 @@
 
 #define KT_SPKUP 15
 #define SPK_SYNTH_TIMEOUT 100000 /* in micro-seconds */
+#define SYNTH_DEFAULT_DEV "ttyS0"
+#define SYNTH_DEFAULT_SER 0
 
 const struct old_serial_port *spk_serial_init(int index);
 void spk_stop_serial_interrupt(void);

drivers/staging/speakup/spk_ttyio.c +4 -0

@@ -7,6 +7,10 @@
 #include "spk_types.h"
 #include "spk_priv.h"
 
+#define DEV_PREFIX_LP "lp"
+
+const char *lp_supported[] = { "acntsa", "bns", "dummy", "txprt" };
+
 struct spk_ldisc_data {
 	char buf;
 	struct semaphore sem;

Quoted 2 lines · Okash Khawaja

This patch adds functionality to validate and convert either a device name or 'ser' member of synth into dev_t.

Quoted 1 line

--- a/drivers/staging/speakup/spk_ttyio.c

drivers/staging/speakup/spk_ttyio.c struct spk_ldisc_data { · line 27

Quoted 5 lines

drivers/staging/speakup/spk_ttyio.c +5 -0

+int ser_to_dev(int ser, dev_t *dev_no)
+{
+	if (ser < 0 || ser > (255 - 64)) {
+                pr_err("speakup: Invalid ser param. \
+				Must be between 0 and 191 inclusive.\n");

As Andy pointed out, never do this for a C string, it's not doing what you think it is :)

Worse case, do this like the following:

		pr_err("speakup: Invalid ser param."
			"Must be between 0 and 191 inclusive.\n");

Quoted 3 lines · Greg Kroah-Hartman

Quoted 2 lines · Okash Khawaja

This patch adds functionality to validate and convert either a device name or 'ser' member of synth into dev_t.

[]

Quoted 1 line

Quoted 1 line

--- a/drivers/staging/speakup/spk_ttyio.c

[]

Quoted 8 lines

drivers/staging/speakup/spk_ttyio.c struct spk_ldisc_data { · line 27

Quoted 5 lines

drivers/staging/speakup/spk_ttyio.c +5 -0

+int ser_to_dev(int ser, dev_t *dev_no)
+{
+	if (ser < 0 || ser > (255 - 64)) {
+                pr_err("speakup: Invalid ser param. \
+				Must be between 0 and 191 inclusive.\n");

As Andy pointed out, never do this for a C string, it's not doing what you think it is :)

Well, some guy.

Quoted 3 lines

Worse case, do this like the following:

		pr_err("speakup: Invalid ser param."
			"Must be between 0 and 191 inclusive.\n");

Nope, now there's no space between param and Must.

Using string concatenation on multiple lines is error prone.

drivers/staging/speakup/spk_ttyio.c struct spk_ldisc_data { · line 27

Quoted 5 lines

drivers/staging/speakup/spk_ttyio.c +5 -0

+int ser_to_dev(int ser, dev_t *dev_no)
+{
+	if (ser < 0 || ser > (255 - 64)) {
+                pr_err("speakup: Invalid ser param. \
+				Must be between 0 and 191 inclusive.\n");

As Andy pointed out, never do this for a C string, it's not doing what you think it is :)

Worse case, do this like the following:

		pr_err("speakup: Invalid ser param."
			"Must be between 0 and 191 inclusive.\n");

Also note, you are using spaces here in the patch, always run checkpatch.pl on your patches, so you don't get a grumpy maintainer telling you to run checkpatch.pl on your patches :)

This doesn't have actual parameter name.
Btw, I would drop dev_ suffix completely from parameter (you have it in function name).

Quoted 1 line

+ * Locking: this acquires tty_mutex

...and releases.

Perhaps it makes sense to describe what it protects (like it's done in some functions around).

Quoted 2 lines

+ */
+int tty_dev_name_to_number(char *dev_name, dev_t *dev_no)

const char *name, right?

Quoted 1 line

+ int rv, index, prefix_length = 0;

I would keep returned variable on a separate line and name it like other functions do in this file, i.e. ret.

int ret;

drivers/tty/tty_io.c static struct tty_driver *get_tty_driver · line 349

Quoted 6 lines

drivers/tty/tty_io.c +6 -0

+       while (!isdigit(*(dev_name + prefix_length)) && prefix_length <
+                       strlen(dev_name) )
+               prefix_length++;
+
+       if (prefix_length == strlen(dev_name))
+               return -EINVAL;

Basically, what you need is to get tailing digits, right?

Moreover, there is quite similar piece of code in
tty_find_polling_driver() you may share.

drivers/tty/tty_io.c static struct tty_driver *get_tty_driver · line 359

Quoted 4 lines

drivers/tty/tty_io.c +3 -0

+                       if (rv) {
 
+                               mutex_unlock(&tty_mutex);
+                               return rv;

I would go with goto style in this function (since it has locking involved).

Quoted 2 lines

+ }

All together kstrtoint() is invariant here as far as I can see and can be done out of locking. Also see above comment how to get line index.