pwm: Create device class for pwm channels
Subsystems (2)
PATCH 1/1 pwm: Create device class for pwm channels
From: David Hsu <[email protected]>
Pwm channels don't send uevents when exported, this change adds the channels to a pwm class and set their device type to pwm_channel so uevents are sent.
To do this properly, the device names need to change to uniquely identify a channel. This change is from pwmN to pwm-(chip->base):N
--- Documentation/pwm.txt | 6 ++++-- drivers/pwm/sysfs.c | 15 ++++++++++++--- 2 files changed, 16 insertions(+), 5 deletions(-)
Note, this patch came from David with his work on a system that has dynamic PWM devices and channels, and we needed some way to tell userspace what is going on when they are added or removed. If anyone knows any other way of doing this that does not involve changing the pwm names, please let us know.
Documentation/pwm.txt +4 -2
@@ -80,9 +80,11 @@ unexport - Unexports a PWM channel from sysfs (write-only). The PWM channels are numbered using a per-chip index from 0 to npwm-1. -When a PWM channel is exported a pwmX directory will be created in the +When a PWM channel is exported a pwm-N:X directory will be created in the pwmchipN directory it is associated with, where X is the number of the -channel that was exported. The following properties will then be available: +channel that was exported. It will also be exposed at /sys/class/pwm/ and +can be identified by the pwm_channel device type. +The following properties will then be available: period - The total period of the PWM signal (read/write). Value is in nanoseconds and is the sum of the active and inactive
drivers/pwm/sysfs.c +12 -3
@@ -23,6 +23,8 @@#include <linux/kdev_t.h> #include <linux/pwm.h> +static struct class pwm_class; +struct pwm_export {struct device child;struct pwm_device *pwm;
@@ -222,6 +224,10 @@ static struct attribute *pwm_attrs[] = { };ATTRIBUTE_GROUPS (pwm); +static const struct device_type pwm_channel_type = { + .name ="pwm_channel" , +}; +static void pwm_export_release (struct device *child) {struct pwm_export *export =child_to_pwm_export (child);
@@ -231,6 +237,7 @@ static void pwm_export_release(struct device *child)static int pwm_export_child (struct device *parent,struct pwm_device *pwm) { +struct pwm_chip *chip =dev_get_drvdata (parent);struct pwm_export *export;int ret;
@@ -248,9 +255,11 @@ static int pwm_export_child(struct device *parent, struct pwm_device *pwm) export->child.release = pwm_export_release; export->child.parent = parent; + export->child.type = &pwm_channel_type; export->child.devt =MKDEV (0 ,0 ); + export->child.class = &pwm_class; export->child.groups = pwm_groups; -dev_set_name (&export->child,"pwm%u" , pwm->hwpwm); +dev_set_name (&export->child,"pwm-%d:%u" , chip->base, pwm->hwpwm); ret =device_register (&export->child);if (ret) {
@@ -355,7 +364,6 @@ ATTRIBUTE_GROUPS(pwm_chip);static struct class pwm_class = { .name ="pwm" , .owner =THIS_MODULE , - .dev_groups = pwm_chip_groups, };static int pwmchip_sysfs_match (struct device *parent,const void *data)
@@ -371,7 +379,8 @@ void pwmchip_sysfs_export(struct pwm_chip *chip)* If device_create() fails the pwm_chip is still usable by * the kernel its just not exported. */ - parent =device_create (&pwm_class, chip->dev,MKDEV (0 ,0 ), chip, + parent =device_create_with_groups (&pwm_class, chip->dev,MKDEV (0 ,0 ), + chip, pwm_chip_groups,"pwmchip%d" , chip->base);if (IS_ERR (parent)) { dev_warn(chip->dev,
Quoted 16 lines · Greg KH
From: David Hsu <[email protected]>
Pwm channels don't send uevents when exported, this change adds the channels to a pwm class and set their device type to
pwm_channelso uevents are sent.To do this properly, the device names need to change to uniquely identify a channel. This change is from pwmN to pwm-(chip->base):N
Signed-off-by David Hsu <[email protected]>Signed-off-by Greg Kroah-Hartman <[email protected]>--- Documentation/pwm.txt | 6 ++++-- drivers/pwm/sysfs.c | 15 ++++++++++++--- 2 files changed, 16 insertions(+), 5 deletions(-)
Quoted 5 lines
Note, this patch came from David with his work on a system that has dynamic PWM devices and channels, and we needed some way to tell userspace what is going on when they are added or removed. If anyone knows any other way of doing this that does not involve changing the pwm names, please let us know.
Is it truly PWM channels that dynamically appear and disappear? I'd be interested in how that's achieved, because there are probably other issues that will manifest if you do that. Do you have a pointer to the work that David's been undertaking? Generally some more context on the use-case would be helpful here.
Also I'd prefer if this avoided using chip->base here, because it exists purely for legacy purposes and is supposed to go away eventually.
Thierry
Quoted 23 lines · Thierry Reding
Quoted 16 lines · Greg KH
From: David Hsu <[email protected]>
Pwm channels don't send uevents when exported, this change adds the channels to a pwm class and set their device type to
pwm_channelso uevents are sent.To do this properly, the device names need to change to uniquely identify a channel. This change is from pwmN to pwm-(chip->base):N
Signed-off-by David Hsu <[email protected]>Signed-off-by Greg Kroah-Hartman <[email protected]>--- Documentation/pwm.txt | 6 ++++-- drivers/pwm/sysfs.c | 15 ++++++++++++--- 2 files changed, 16 insertions(+), 5 deletions(-)Quoted 5 lines
Note, this patch came from David with his work on a system that has dynamic PWM devices and channels, and we needed some way to tell userspace what is going on when they are added or removed. If anyone knows any other way of doing this that does not involve changing the pwm names, please let us know.
Quoted 5 lines
Is it truly PWM channels that dynamically appear and disappear? I'd be interested in how that's achieved, because there are probably other issues that will manifest if you do that. Do you have a pointer to the work that David's been undertaking? Generally some more context on the use-case would be helpful here.
Only PWM devices are dynamic, the number of channels exposed by devices do not change after they've been added to the system.
Quoted 5 lines
Also I'd prefer if this avoided using
chip->basehere, because it exists purely for legacy purposes and is supposed to go away eventually.Thierry
Would using dev_name(parent) be an acceptable alternative?
Thanks,
David
Quoted 35 lines · David Hsu
Quoted 23 lines · Thierry Reding
Quoted 16 lines · Greg KH
From: David Hsu <[email protected]>
Pwm channels don't send uevents when exported, this change adds the channels to a pwm class and set their device type to
pwm_channelso uevents are sent.To do this properly, the device names need to change to uniquely identify a channel. This change is from pwmN to pwm-(chip->base):N
Signed-off-by David Hsu <[email protected]>Signed-off-by Greg Kroah-Hartman <[email protected]>--- Documentation/pwm.txt | 6 ++++-- drivers/pwm/sysfs.c | 15 ++++++++++++--- 2 files changed, 16 insertions(+), 5 deletions(-)Quoted 5 lines
Note, this patch came from David with his work on a system that has dynamic PWM devices and channels, and we needed some way to tell userspace what is going on when they are added or removed. If anyone knows any other way of doing this that does not involve changing the pwm names, please let us know.
Quoted 5 lines
Is it truly PWM channels that dynamically appear and disappear? I'd be interested in how that's achieved, because there are probably other issues that will manifest if you do that. Do you have a pointer to the work that David's been undertaking? Generally some more context on the use-case would be helpful here.
Only PWM devices are dynamic, the number of channels exposed by devices do not change after they've been added to the system.
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Also I'd prefer if this avoided using
chip->basehere, because it exists purely for legacy purposes and is supposed to go away eventually.Thierry
Would using
dev_name(parent)be an acceptable alternative?
Ping! Any comments on the above?
Thanks,
David
Quoted 25 lines · David Hsu
Quoted 23 lines · Thierry Reding
Quoted 21 lines · Greg KH
From: David Hsu <[email protected]>
Pwm channels don't send uevents when exported, this change adds the channels to a pwm class and set their device type to
pwm_channelso uevents are sent.To do this properly, the device names need to change to uniquely identify a channel. This change is from pwmN to pwm-(chip->base):N
Signed-off-by David Hsu <[email protected]>Signed-off-by Greg Kroah-Hartman <[email protected]>--- Documentation/pwm.txt | 6 ++++-- drivers/pwm/sysfs.c | 15 ++++++++++++--- 2 files changed, 16 insertions(+), 5 deletions(-)Note, this patch came from David with his work on a system that has dynamic PWM devices and channels, and we needed some way to tell userspace what is going on when they are added or removed. If anyone knows any other way of doing this that does not involve changing the pwm names, please let us know.
Quoted 8 lines
Quoted 5 lines
Is it truly PWM channels that dynamically appear and disappear? I'd be interested in how that's achieved, because there are probably other issues that will manifest if you do that. Do you have a pointer to the work that David's been undertaking? Generally some more context on the use-case would be helpful here.
Only PWM devices are dynamic, the number of channels exposed by devices do not change after they've been added to the system.
In that case, would it not be enough to use the uevents generated by the addition and removal of the PWM chip devices to/from sysfs?
Quoted 6 lines
Quoted 4 lines
Also I'd prefer if this avoided using
chip->basehere, because it exists purely for legacy purposes and is supposed to go away eventually.Thierry
Would using
dev_name(parent)be an acceptable alternative?
Yes, that sounds like a more sensible choice to me.
Thierry
Quoted 32 lines · Thierry Reding
Quoted 31 lines · David Hsu
Quoted 28 lines · Thierry Reding
Quoted 16 lines · Greg KH
From: David Hsu <[email protected]>
Pwm channels don't send uevents when exported, this change adds the channels to a pwm class and set their device type to
pwm_channelso uevents are sent.To do this properly, the device names need to change to uniquely identify a channel. This change is from pwmN to pwm-(chip->base):N
Signed-off-by David Hsu <[email protected]>Signed-off-by Greg Kroah-Hartman <[email protected]>--- Documentation/pwm.txt | 6 ++++-- drivers/pwm/sysfs.c | 15 ++++++++++++--- 2 files changed, 16 insertions(+), 5 deletions(-)Quoted 5 lines
Note, this patch came from David with his work on a system that has dynamic PWM devices and channels, and we needed some way to tell userspace what is going on when they are added or removed. If anyone knows any other way of doing this that does not involve changing the pwm names, please let us know.
Is it truly PWM channels that dynamically appear and disappear? I'd be interested in how that's achieved, because there are probably other issues that will manifest if you do that. Do you have a pointer to the work that David's been undertaking? Generally some more context on the use-case would be helpful here.
Quoted 5 lines
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Only PWM devices are dynamic, the number of channels exposed by devices do not change after they've been added to the system.
In that case, would it not be enough to use the uevents generated by the addition and removal of the PWM chip devices to/from sysfs?
We need channel level granularity to modify permissions for sysfs nodes that are created when the channels are exported.
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Also I'd prefer if this avoided using
chip->basehere, because it exists purely for legacy purposes and is supposed to go away eventually.Thierry
Would using
dev_name(parent)be an acceptable alternative?Yes, that sounds like a more sensible choice to me.
Thanks Thierry, I'll send out a v2 shortly.
It also occurred to me that this change could affect apps that have the previous name hard coded. I can create a link pointing to the new name but wanted to see if there's a better recommendation or if it's required.
David
Quoted 2 lines
Thierry