| Message ID | 20180501094553.31545-1-lee.jones@linaro.org |
|---|---|
| State | Accepted |
| Commit | 1768391c3674b0c6bdc4947121f15fb0c2f47ec4 |
| Headers | show |
| Series | [1/1] mfd: tps65911-comparator: Fix an off by one bug | expand |
On 01/05/18 10:45, Lee Jones wrote: > The COMP1 and COMP2 elements are in 0 and 1 respectively so this code is > accessing the wrong elements and one space beyond the end of the array. > > The "id" variable is never COMP (0) so that code can be removed. > > Fixes: 6851ad3ab346 ("TPS65911: Comparator: Add comparator driver") > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > Signed-off-by: Lee Jones <lee.jones@linaro.org> > --- > > History: > > Dan was the originator of this patch and the author of the commit log, > but produced 2 code solutions which I wasn't happy with. The first > submission [0] introduced a COMP device, which after a quick check of > the datasheet [1] appeared to be fictitious. A subsequent submission > [2] conducted arithmetic in array indexes. > > It is my belief that the correct solution is to roll which the > situation the hardware engineers presented us with and define COMP1 > at position 0 and COMP2 at position 1 such that we can use the > simplest code possible to select them. > > Dan wasn't happy to put his name to this, which I completely > understand. Calling SOMETHING1 0 (zero) is a little unnatural. > > However, since I have no shame, I offered to submit it. As an idly-curious passer-by, this looks perfectly reasonable to me - I don't see why a mapping between names and indices should have to be artificially constrained just because the names happen to contain numerals. If it's really that abhorrent, then I guess they could be named something like COMPn_ID for even more clarity. That said, now that I've gone and looked, the whole business seems ridiculously over-engineered. AFAICS it would be infinitely simpler to just pass the register address directly where id is currently passed, statically define UV_MAX, and get rid of the otherwise-pointless struct comparator entirely. The current abstraction doesn't look like it could actually scale to support different chips without major surgery anyway. Robin. > [0] https://lkml.org/lkml/2018/4/19/449 > [1] http://www.ti.com/lit/ds/symlink/tps65911.pdf (page 52) > [2] https://lkml.org/lkml/2018/4/20/204 > > drivers/mfd/tps65911-comparator.c | 11 ++--------- > 1 file changed, 2 insertions(+), 9 deletions(-) > > diff --git a/drivers/mfd/tps65911-comparator.c b/drivers/mfd/tps65911-comparator.c > index d223857fb4ad..33591767fb9b 100644 > --- a/drivers/mfd/tps65911-comparator.c > +++ b/drivers/mfd/tps65911-comparator.c > @@ -22,9 +22,8 @@ > #include <linux/gpio.h> > #include <linux/mfd/tps65910.h> > > -#define COMP 0 > -#define COMP1 1 > -#define COMP2 2 > +#define COMP1 0 > +#define COMP2 1 > > /* Comparator 1 voltage selection table in millivolts */ > static const u16 COMP_VSEL_TABLE[] = { > @@ -63,9 +62,6 @@ static int comp_threshold_set(struct tps65910 *tps65910, int id, int voltage) > int ret; > u8 index = 0, val; > > - if (id == COMP) > - return 0; > - > while (curr_voltage < tps_comp.uV_max) { > curr_voltage = tps_comp.vsel_table[index]; > if (curr_voltage >= voltage) > @@ -89,9 +85,6 @@ static int comp_threshold_get(struct tps65910 *tps65910, int id) > unsigned int val; > int ret; > > - if (id == COMP) > - return 0; > - > ret = tps65910_reg_read(tps65910, tps_comp.reg, &val); > if (ret < 0) > return ret; >
The background is that no one noticed that this driver stopped being buildable in 2012 until I fixed it last week. This is the third proposed patch to fix the off by one. All three patches fix the bug, but Lee refused to accept my style and I refused to use Lee's style... Absolutely *no way*! LOL. But really neither of us take it personally and we've met in person before and collaborate over email and get along. This thread has been pretty amusing for me, but let's move on. :P regards, dan carpenter
On Tue, 01 May 2018, Robin Murphy wrote: > On 01/05/18 10:45, Lee Jones wrote: > > The COMP1 and COMP2 elements are in 0 and 1 respectively so this code is > > accessing the wrong elements and one space beyond the end of the array. > > > > The "id" variable is never COMP (0) so that code can be removed. > > > > Fixes: 6851ad3ab346 ("TPS65911: Comparator: Add comparator driver") > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > > Signed-off-by: Lee Jones <lee.jones@linaro.org> > > --- > > > > History: > > > > Dan was the originator of this patch and the author of the commit log, > > but produced 2 code solutions which I wasn't happy with. The first > > submission [0] introduced a COMP device, which after a quick check of > > the datasheet [1] appeared to be fictitious. A subsequent submission > > [2] conducted arithmetic in array indexes. > > > > It is my belief that the correct solution is to roll which the > > situation the hardware engineers presented us with and define COMP1 > > at position 0 and COMP2 at position 1 such that we can use the > > simplest code possible to select them. > > > > Dan wasn't happy to put his name to this, which I completely > > understand. Calling SOMETHING1 0 (zero) is a little unnatural. > > > > However, since I have no shame, I offered to submit it. > > As an idly-curious passer-by, this looks perfectly reasonable to me - I > don't see why a mapping between names and indices should have to be > artificially constrained just because the names happen to contain numerals. Right. This was my thinking too. > If it's really that abhorrent, then I guess they could be named something > like COMPn_ID for even more clarity. > > That said, now that I've gone and looked, the whole business seems > ridiculously over-engineered. AFAICS it would be infinitely simpler to just > pass the register address directly where id is currently passed, statically > define UV_MAX, and get rid of the otherwise-pointless struct comparator > entirely. The current abstraction doesn't look like it could actually scale > to support different chips without major surgery anyway. Sounds good. Patches always welcome. ;) -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
On Tue, 01 May 2018, Dan Carpenter wrote: > The background is that no one noticed that this driver stopped being > buildable in 2012 until I fixed it last week. This is the third > proposed patch to fix the off by one. All three patches fix the bug, > but Lee refused to accept my style and I refused to use Lee's style... > Absolutely *no way*! LOL. But really neither of us take it personally > and we've met in person before and collaborate over email and get along. > > This thread has been pretty amusing for me, but let's move on. :P +999 Plan is to let it sit for a week or so. Give some more idle passers-by to have their say. Then I'll merge it regardless (/me jokes). -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
diff --git a/drivers/mfd/tps65911-comparator.c b/drivers/mfd/tps65911-comparator.c index d223857fb4ad..33591767fb9b 100644 --- a/drivers/mfd/tps65911-comparator.c +++ b/drivers/mfd/tps65911-comparator.c @@ -22,9 +22,8 @@ #include <linux/gpio.h> #include <linux/mfd/tps65910.h> -#define COMP 0 -#define COMP1 1 -#define COMP2 2 +#define COMP1 0 +#define COMP2 1 /* Comparator 1 voltage selection table in millivolts */ static const u16 COMP_VSEL_TABLE[] = { @@ -63,9 +62,6 @@ static int comp_threshold_set(struct tps65910 *tps65910, int id, int voltage) int ret; u8 index = 0, val; - if (id == COMP) - return 0; - while (curr_voltage < tps_comp.uV_max) { curr_voltage = tps_comp.vsel_table[index]; if (curr_voltage >= voltage) @@ -89,9 +85,6 @@ static int comp_threshold_get(struct tps65910 *tps65910, int id) unsigned int val; int ret; - if (id == COMP) - return 0; - ret = tps65910_reg_read(tps65910, tps_comp.reg, &val); if (ret < 0) return ret;
The COMP1 and COMP2 elements are in 0 and 1 respectively so this code is accessing the wrong elements and one space beyond the end of the array. The "id" variable is never COMP (0) so that code can be removed. Fixes: 6851ad3ab346 ("TPS65911: Comparator: Add comparator driver") Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Lee Jones <lee.jones@linaro.org> --- History: Dan was the originator of this patch and the author of the commit log, but produced 2 code solutions which I wasn't happy with. The first submission [0] introduced a COMP device, which after a quick check of the datasheet [1] appeared to be fictitious. A subsequent submission [2] conducted arithmetic in array indexes. It is my belief that the correct solution is to roll which the situation the hardware engineers presented us with and define COMP1 at position 0 and COMP2 at position 1 such that we can use the simplest code possible to select them. Dan wasn't happy to put his name to this, which I completely understand. Calling SOMETHING1 0 (zero) is a little unnatural. However, since I have no shame, I offered to submit it. [0] https://lkml.org/lkml/2018/4/19/449 [1] http://www.ti.com/lit/ds/symlink/tps65911.pdf (page 52) [2] https://lkml.org/lkml/2018/4/20/204 drivers/mfd/tps65911-comparator.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) -- 2.17.0