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eeprom: at24: correctly set the size for at24mac402

PATCH In review Bartosz Golaszewski 4 participants 6 messages Nov 27, 2017 – Dec 4, 2017

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Stable branch Char and misc drivers I2C subsystem host drivers
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Bartosz Golaszewski

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#0 lore raw

PATCH 1/1 eeprom: at24: correctly set the size for at24mac402

There's an ilog2() expansion in AT24_DEVICE_MAGIC() which rounds down the actual size of EUI-48 byte array in at24mac402 eeproms to 4 from 6, making it impossible to read it all.

Fix it by manually adjusting the value in probe().

This patch contains a temporary fix that is suitable for stable branches. Eventually we'll probably remove the call to ilog2() while converting the magic values to actual structs.

Cc [email protected]
Fixes 0b813658c115 ("eeprom: at24: add support for at24mac series")
Signed-off-by Bartosz Golaszewski <[email protected]>
---
 drivers/misc/eeprom/at24.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
drivers/misc/eeprom/at24.c +10 -0
index e0b4b36ef010..783244b485cc 100644
@@ -730,6 +730,16 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 		dev_warn(&client->dev,
 			"page_size looks suspicious (no power of 2)!\n");
 
+	/*
+	 * REVISIT: the size of the EUI-48 byte array is 6 in at24mac402, while
+	 * the call to ilog2() in AT24_DEVICE_MAGIC() rounds it down to 4.
+	 *
+	 * Eventually we'll get rid of the magic values altoghether in favor of
+	 * real structs, but for now just manually set the right size.
+	 */
+	if (chip.flags & AT24_FLAG_MAC && chip.byte_len == 4)
+		chip.byte_len = 6;
+
 	/* Use I2C operations unless we're stuck with SMBus extensions. */
 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 		if (chip.flags & AT24_FLAG_ADDR16)
Signature · 1 line
2.15.0
#1 lore raw
Quoted 10 lines · Bartosz Golaszewski

There's an ilog2() expansion in AT24_DEVICE_MAGIC() which rounds down the actual size of EUI-48 byte array in at24mac402 eeproms to 4 from 6, making it impossible to read it all.

Fix it by manually adjusting the value in probe().

This patch contains a temporary fix that is suitable for stable branches. Eventually we'll probably remove the call to ilog2() while converting the magic values to actual structs.

drivers/misc/eeprom/at24.c static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) · line 740

Quoted 8 lines
drivers/misc/eeprom/at24.c +8 -0
+       /*
+        * REVISIT: the size of the EUI-48 byte array is 6 in at24mac402, while
+        * the call to ilog2() in AT24_DEVICE_MAGIC() rounds it down to 4.
+        *
+        * Eventually we'll get rid of the magic values altoghether in favor of
+        * real structs, but for now just manually set the right size.
+        */
+       if (chip.flags & AT24_FLAG_MAC && chip.byte_len == 4)

I didn't check, but do we need to test for len == 4 at all?

Quoted 1 line

+ chip.byte_len = 6;

Signature · 2 lines
With Best Regards,
Andy Shevchenko
author
#2 lore raw

2017-11-28 11:25 GMT+01:00 Andy Shevchenko <[email protected]>:

Quoted 20 lines · Bartosz Golaszewski
Quoted 10 lines

There's an ilog2() expansion in AT24_DEVICE_MAGIC() which rounds down the actual size of EUI-48 byte array in at24mac402 eeproms to 4 from 6, making it impossible to read it all.

Fix it by manually adjusting the value in probe().

This patch contains a temporary fix that is suitable for stable branches. Eventually we'll probably remove the call to ilog2() while converting the magic values to actual structs.

drivers/misc/eeprom/at24.c static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) · line 740

Quoted 8 lines
drivers/misc/eeprom/at24.c +8 -0
+       /*
+        * REVISIT: the size of the EUI-48 byte array is 6 in at24mac402, while
+        * the call to ilog2() in AT24_DEVICE_MAGIC() rounds it down to 4.
+        *
+        * Eventually we'll get rid of the magic values altoghether in favor of
+        * real structs, but for now just manually set the right size.
+        */
+       if (chip.flags & AT24_FLAG_MAC && chip.byte_len == 4)
Quoted 7 lines

I didn't check, but do we need to test for len == 4 at all?

Quoted 1 line

+ chip.byte_len = 6;

--
With Best Regards,
Andy Shevchenko

Yes, because the fix is only relevant for at24mac402 whose MAC byte array is 6 bytes long, while the one in at24mac602 is 8 bytes and the driver doesn't truncate the byte_len for it.

Thanks,
Bartosz

#3 lore raw
Quoted 25 lines · Bartosz Golaszewski

2017-11-28 11:25 GMT+01:00 Andy Shevchenko <[email protected]>:

Quoted 24 lines · Bartosz Golaszewski
Quoted 10 lines

There's an ilog2() expansion in AT24_DEVICE_MAGIC() which rounds down the actual size of EUI-48 byte array in at24mac402 eeproms to 4 from 6, making it impossible to read it all.

Fix it by manually adjusting the value in probe().

This patch contains a temporary fix that is suitable for stable branches. Eventually we'll probably remove the call to ilog2() while converting the magic values to actual structs.

drivers/misc/eeprom/at24.c static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) · line 740

Quoted 8 lines
drivers/misc/eeprom/at24.c +8 -0
+       /*
+        * REVISIT: the size of the EUI-48 byte array is 6 in at24mac402, while
+        * the call to ilog2() in AT24_DEVICE_MAGIC() rounds it down to 4.
+        *
+        * Eventually we'll get rid of the magic values altoghether in favor of
+        * real structs, but for now just manually set the right size.
+        */
+       if (chip.flags & AT24_FLAG_MAC && chip.byte_len == 4)

I didn't check, but do we need to test for len == 4 at all?

Quoted 1 line

+ chip.byte_len = 6;

Quoted 8 lines
Quoted 3 lines

--
With Best Regards,
Andy Shevchenko

Yes, because the fix is only relevant for at24mac402 whose MAC byte array is 6 bytes long, while the one in at24mac602 is 8 bytes and the driver doesn't truncate the byte_len for it.
From my point of view, I think all chips in at24_ids[] array should be checked

about restrictions regarding the size truncation (especially the ones from the initial commit: "2b7a5056a0a7ff17d5d2 i2c: New-style EEPROM driver using device IDs" which introduces AT24_DEVICE_MAGIC() macro) and if none of them has such restrictions we should get rid of the ilog2() restrictions.

Just my 2 cents...
Claudiu

Quoted 4 lines

Thanks,
Bartosz

Reviewed-by on v1 1/1
#4 lore raw
In reply to Bartosz Golaszewski
Quoted 10 lines · Bartosz Golaszewski

There's an ilog2() expansion in AT24_DEVICE_MAGIC() which rounds down the actual size of EUI-48 byte array in at24mac402 eeproms to 4 from 6, making it impossible to read it all.

Fix it by manually adjusting the value in probe().

This patch contains a temporary fix that is suitable for stable branches. Eventually we'll probably remove the call to ilog2() while converting the magic values to actual structs.

Reviewed-by Andy Shevchenko <[email protected]>
Quoted 31 lines
Cc [email protected]
Fixes 0b813658c115 ("eeprom: at24: add support for at24mac series")
Signed-off-by Bartosz Golaszewski <[email protected]>
---
 drivers/misc/eeprom/at24.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
drivers/misc/eeprom/at24.c +10 -1
index e0b4b36ef010..783244b485cc 100644
@@ -730,6 +730,16 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
                dev_warn(&client->dev,
                        "page_size looks suspicious (no power of 2)!\n");
 
+       /*
+        * REVISIT: the size of the EUI-48 byte array is 6 in at24mac402, while
+        * the call to ilog2() in AT24_DEVICE_MAGIC() rounds it down to 4.
+        *
+        * Eventually we'll get rid of the magic values altoghether in favor of
+        * real structs, but for now just manually set the right size.
+        */
+       if (chip.flags & AT24_FLAG_MAC && chip.byte_len == 4)
+               chip.byte_len = 6;
+
        /* Use I2C operations unless we're stuck with SMBus extensions. */
        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
                if (chip.flags & AT24_FLAG_ADDR16)
--

2.15.0

Signature · 2 lines
With Best Regards,
Andy Shevchenko
#5 lore raw

Am 28.11.2017 um 13:09 schrieb Andy Shevchenko:

Quoted 5 lines · Bartosz Golaszewski
Quoted 4 lines

There's an ilog2() expansion in AT24_DEVICE_MAGIC() which rounds down the actual size of EUI-48 byte array in at24mac402 eeproms to 4 from 6, making it impossible to read it all.

Quoted 9 lines
Quoted 6 lines

Fix it by manually adjusting the value in probe().

This patch contains a temporary fix that is suitable for stable branches. Eventually we'll probably remove the call to ilog2() while converting the magic values to actual structs.

Reviewed-by Andy Shevchenko <[email protected]>

Looks good also to me.

Quoted 34 lines
Quoted 31 lines
Cc [email protected]
Fixes 0b813658c115 ("eeprom: at24: add support for at24mac series")
Signed-off-by Bartosz Golaszewski <[email protected]>
---
 drivers/misc/eeprom/at24.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
drivers/misc/eeprom/at24.c +10 -1
index e0b4b36ef010..783244b485cc 100644
@@ -730,6 +730,16 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
                dev_warn(&client->dev,
                        "page_size looks suspicious (no power of 2)!\n");
 
+       /*
+        * REVISIT: the size of the EUI-48 byte array is 6 in at24mac402, while
+        * the call to ilog2() in AT24_DEVICE_MAGIC() rounds it down to 4.
+        *
+        * Eventually we'll get rid of the magic values altoghether in favor of
+        * real structs, but for now just manually set the right size.
+        */
+       if (chip.flags & AT24_FLAG_MAC && chip.byte_len == 4)
+               chip.byte_len = 6;
+
        /* Use I2C operations unless we're stuck with SMBus extensions. */
        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
                if (chip.flags & AT24_FLAG_ADDR16)
--

2.15.0