| Message ID | 20171127122808.21042-1-brgl@bgdev.pl |
|---|---|
| State | Rejected |
| Delegated to: | Bartosz Golaszewski |
| Headers | show |
| Series | eeprom: at24: fix the magic value for at24mac402 | expand |
Am 27.11.2017 um 13:28 schrieb 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 creating the magic value manually with the correct size. > > 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. > > This fix will cause a warning message to be emitted by probe() for > at24mac402 chips but theys should be initialized correctly anyway. > > Cc: stable@vger.kernel.org > Fixes: 0b813658c115 ("eeprom: at24: add support for at24mac series") > Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl> > --- > drivers/misc/eeprom/at24.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c > index e0b4b36ef010..72adf34627f5 100644 > --- a/drivers/misc/eeprom/at24.c > +++ b/drivers/misc/eeprom/at24.c > @@ -141,8 +141,17 @@ static const struct i2c_device_id at24_ids[] = { > { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) }, > { "24cs02", AT24_DEVICE_MAGIC(16, > AT24_FLAG_SERIAL | AT24_FLAG_READONLY) }, > - { "24mac402", AT24_DEVICE_MAGIC(48 / 8, > - AT24_FLAG_MAC | AT24_FLAG_READONLY) }, > + /* > + * 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. We > + * might want to eventually remove it altogether or maybe even convert > + * the magic values to real structs. > + * > + * For now just create the magic value manually with the right size. > + */ > + { "24mac402", ((1 << AT24_SIZE_FLAGS | > + (AT24_FLAG_MAC | AT24_FLAG_READONLY)) > + << AT24_SIZE_BYTELEN | (48 / 8)) }, > { "24mac602", AT24_DEVICE_MAGIC(64 / 8, > AT24_FLAG_MAC | AT24_FLAG_READONLY) }, > /* spd is a 24c02 in memory DIMMs */ > I'm afraid this won't work. byte_len = BIT(least 5 bits of magic value) Means byte_len for 24mac402 would be BIT(6) = 64 with your patch. What we could do, although it seems to be quite ugly: round up the ilog2 value. Instead of ilog2(_len) we could use ilog2((_len) * 2 - 1) Rgds, Heiner
2017-11-27 20:15 GMT+01:00 Heiner Kallweit <hkallweit1@gmail.com>: > Am 27.11.2017 um 13:28 schrieb 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 creating the magic value manually with the correct size. >> >> 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. >> >> This fix will cause a warning message to be emitted by probe() for >> at24mac402 chips but theys should be initialized correctly anyway. >> >> Cc: stable@vger.kernel.org >> Fixes: 0b813658c115 ("eeprom: at24: add support for at24mac series") >> Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl> >> --- >> drivers/misc/eeprom/at24.c | 13 +++++++++++-- >> 1 file changed, 11 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c >> index e0b4b36ef010..72adf34627f5 100644 >> --- a/drivers/misc/eeprom/at24.c >> +++ b/drivers/misc/eeprom/at24.c >> @@ -141,8 +141,17 @@ static const struct i2c_device_id at24_ids[] = { >> { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) }, >> { "24cs02", AT24_DEVICE_MAGIC(16, >> AT24_FLAG_SERIAL | AT24_FLAG_READONLY) }, >> - { "24mac402", AT24_DEVICE_MAGIC(48 / 8, >> - AT24_FLAG_MAC | AT24_FLAG_READONLY) }, >> + /* >> + * 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. We >> + * might want to eventually remove it altogether or maybe even convert >> + * the magic values to real structs. >> + * >> + * For now just create the magic value manually with the right size. >> + */ >> + { "24mac402", ((1 << AT24_SIZE_FLAGS | >> + (AT24_FLAG_MAC | AT24_FLAG_READONLY)) >> + << AT24_SIZE_BYTELEN | (48 / 8)) }, >> { "24mac602", AT24_DEVICE_MAGIC(64 / 8, >> AT24_FLAG_MAC | AT24_FLAG_READONLY) }, >> /* spd is a 24c02 in memory DIMMs */ >> > I'm afraid this won't work. byte_len = BIT(least 5 bits of magic value) > Means byte_len for 24mac402 would be BIT(6) = 64 with your patch. > > What we could do, although it seems to be quite ugly: round up the ilog2 > value. Instead of ilog2(_len) we could use ilog2((_len) * 2 - 1) > > Rgds, Heiner This is exactly why we should get rid of these magic values. ;) Thanks for spotting that. Another (slightly cleaner) solution that comes to mind is checking the eeprom type in probe and adjusting byte_len manually. Thanks, Bartosz
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c index e0b4b36ef010..72adf34627f5 100644 --- a/drivers/misc/eeprom/at24.c +++ b/drivers/misc/eeprom/at24.c @@ -141,8 +141,17 @@ static const struct i2c_device_id at24_ids[] = { { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) }, { "24cs02", AT24_DEVICE_MAGIC(16, AT24_FLAG_SERIAL | AT24_FLAG_READONLY) }, - { "24mac402", AT24_DEVICE_MAGIC(48 / 8, - AT24_FLAG_MAC | AT24_FLAG_READONLY) }, + /* + * 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. We + * might want to eventually remove it altogether or maybe even convert + * the magic values to real structs. + * + * For now just create the magic value manually with the right size. + */ + { "24mac402", ((1 << AT24_SIZE_FLAGS | + (AT24_FLAG_MAC | AT24_FLAG_READONLY)) + << AT24_SIZE_BYTELEN | (48 / 8)) }, { "24mac602", AT24_DEVICE_MAGIC(64 / 8, AT24_FLAG_MAC | AT24_FLAG_READONLY) }, /* spd is a 24c02 in memory DIMMs */
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 creating the magic value manually with the correct size. 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. This fix will cause a warning message to be emitted by probe() for at24mac402 chips but theys should be initialized correctly anyway. Cc: stable@vger.kernel.org Fixes: 0b813658c115 ("eeprom: at24: add support for at24mac series") Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl> --- drivers/misc/eeprom/at24.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)