[Qemu-devel] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Qemu-devel] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[BALATON Zoltan]

Division with round up is the correct way to compute this even if the
only case where division with round down gives incorrect result is
probably 15 bpp. This case was explicitely patched up in one of these
functions but was unhandled in the other. (I'm not sure about setting
16 bpp for the 15bpp case either but I left that there for now.)

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
  console.c |    5 ++---
  1 file changed, 2 insertions(+), 3 deletions(-)

  v2: Use DIV_ROUND_UP and extended commit message

diff --git a/console.c b/console.c
index 4525cc7..9df1701 100644
--- a/console.c
+++ b/console.c
@@ -1612,7 +1612,7 @@ PixelFormat qemu_different_endianness_pixelformat(int bpp)
      memset(&pf, 0x00, sizeof(PixelFormat));

      pf.bits_per_pixel = bpp;
-    pf.bytes_per_pixel = bpp / 8;
+    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
      pf.depth = bpp == 32 ? 24 : bpp;

      switch (bpp) {
@@ -1661,13 +1661,12 @@ PixelFormat qemu_default_pixelformat(int bpp)
      memset(&pf, 0x00, sizeof(PixelFormat));

      pf.bits_per_pixel = bpp;
-    pf.bytes_per_pixel = bpp / 8;
+    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
      pf.depth = bpp == 32 ? 24 : bpp;

      switch (bpp) {
          case 15:
              pf.bits_per_pixel = 16;
-            pf.bytes_per_pixel = 2;
              pf.rmask = 0x00007c00;
              pf.gmask = 0x000003E0;
              pf.bmask = 0x0000001F;
-- 
1.7.10

Re: [Qemu-devel] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Jan Kiszka]

On 2012-08-22 17:19, BALATON Zoltan wrote:
> Division with round up is the correct way to compute this even if the
> only case where division with round down gives incorrect result is
> probably 15 bpp. This case was explicitely patched up in one of these
> functions but was unhandled in the other. (I'm not sure about setting
> 16 bpp for the 15bpp case either but I left that there for now.)
> 
> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> ---
>  console.c |    5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
>  v2: Use DIV_ROUND_UP and extended commit message
> 
> diff --git a/console.c b/console.c
> index 4525cc7..9df1701 100644
> --- a/console.c
> +++ b/console.c
> @@ -1612,7 +1612,7 @@ PixelFormat
> qemu_different_endianness_pixelformat(int bpp)
>      memset(&pf, 0x00, sizeof(PixelFormat));
> 
>      pf.bits_per_pixel = bpp;
> -    pf.bytes_per_pixel = bpp / 8;
> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>      pf.depth = bpp == 32 ? 24 : bpp;
> 
>      switch (bpp) {
> @@ -1661,13 +1661,12 @@ PixelFormat qemu_default_pixelformat(int bpp)
>      memset(&pf, 0x00, sizeof(PixelFormat));
> 
>      pf.bits_per_pixel = bpp;
> -    pf.bytes_per_pixel = bpp / 8;
> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>      pf.depth = bpp == 32 ? 24 : bpp;
> 
>      switch (bpp) {
>          case 15:
>              pf.bits_per_pixel = 16;
> -            pf.bytes_per_pixel = 2;

Removed unintentionally?

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux

Re: [Qemu-devel] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Stefan Weil]

Am 22.08.2012 17:32, schrieb Jan Kiszka:
> On 2012-08-22 17:19, BALATON Zoltan wrote:
>> Division with round up is the correct way to compute this even if the
>> only case where division with round down gives incorrect result is
>> probably 15 bpp. This case was explicitely patched up in one of these
>> functions but was unhandled in the other. (I'm not sure about setting
>> 16 bpp for the 15bpp case either but I left that there for now.)
>>
>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
>> ---
>>   console.c |    5 ++---
>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>
>>   v2: Use DIV_ROUND_UP and extended commit message
>>
>> diff --git a/console.c b/console.c
>> index 4525cc7..9df1701 100644
>> --- a/console.c
>> +++ b/console.c
>> @@ -1612,7 +1612,7 @@ PixelFormat
>> qemu_different_endianness_pixelformat(int bpp)
>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>
>>       pf.bits_per_pixel = bpp;
>> -    pf.bytes_per_pixel = bpp / 8;
>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>       pf.depth = bpp == 32 ? 24 : bpp;
>>
>>       switch (bpp) {
>> @@ -1661,13 +1661,12 @@ PixelFormat qemu_default_pixelformat(int bpp)
>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>
>>       pf.bits_per_pixel = bpp;
>> -    pf.bytes_per_pixel = bpp / 8;
>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>       pf.depth = bpp == 32 ? 24 : bpp;
>>
>>       switch (bpp) {
>>           case 15:
>>               pf.bits_per_pixel = 16;
>> -            pf.bytes_per_pixel = 2;
> Removed unintentionally?
>
> Jan

15 bpp no longer needs special handling because
the computation above is fixed by the same patch,
so the removal is correct.

Stefan

Re: [Qemu-devel] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Jan Kiszka]

On 2012-08-22 18:29, Stefan Weil wrote:
> Am 22.08.2012 17:32, schrieb Jan Kiszka:
>> On 2012-08-22 17:19, BALATON Zoltan wrote:
>>> Division with round up is the correct way to compute this even if the
>>> only case where division with round down gives incorrect result is
>>> probably 15 bpp. This case was explicitely patched up in one of these
>>> functions but was unhandled in the other. (I'm not sure about setting
>>> 16 bpp for the 15bpp case either but I left that there for now.)
>>>
>>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
>>> ---
>>>   console.c |    5 ++---
>>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>>
>>>   v2: Use DIV_ROUND_UP and extended commit message
>>>
>>> diff --git a/console.c b/console.c
>>> index 4525cc7..9df1701 100644
>>> --- a/console.c
>>> +++ b/console.c
>>> @@ -1612,7 +1612,7 @@ PixelFormat
>>> qemu_different_endianness_pixelformat(int bpp)
>>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>>
>>>       pf.bits_per_pixel = bpp;
>>> -    pf.bytes_per_pixel = bpp / 8;
>>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>>       pf.depth = bpp == 32 ? 24 : bpp;
>>>
>>>       switch (bpp) {
>>> @@ -1661,13 +1661,12 @@ PixelFormat qemu_default_pixelformat(int bpp)
>>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>>
>>>       pf.bits_per_pixel = bpp;
>>> -    pf.bytes_per_pixel = bpp / 8;
>>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>>       pf.depth = bpp == 32 ? 24 : bpp;
>>>
>>>       switch (bpp) {
>>>           case 15:
>>>               pf.bits_per_pixel = 16;
>>> -            pf.bytes_per_pixel = 2;
>> Removed unintentionally?
>>
>> Jan
> 
> 15 bpp no longer needs special handling because
> the computation above is fixed by the same patch,
> so the removal is correct.

Ok, actually starting to look at this code: This is apparently a code
cleanup, not a bug fix like the subject suggests. No valid input for
could have actually triggered the round-up issue. Please declare it as
such. Bonus for abort() on the invalid default cases.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux

Re: [Qemu-devel] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Jan Kiszka]

On 2012-08-22 18:44, Jan Kiszka wrote:
> On 2012-08-22 18:29, Stefan Weil wrote:
>> Am 22.08.2012 17:32, schrieb Jan Kiszka:
>>> On 2012-08-22 17:19, BALATON Zoltan wrote:
>>>> Division with round up is the correct way to compute this even if the
>>>> only case where division with round down gives incorrect result is
>>>> probably 15 bpp. This case was explicitely patched up in one of these
>>>> functions but was unhandled in the other. (I'm not sure about setting
>>>> 16 bpp for the 15bpp case either but I left that there for now.)
>>>>
>>>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
>>>> ---
>>>>   console.c |    5 ++---
>>>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>>>
>>>>   v2: Use DIV_ROUND_UP and extended commit message
>>>>
>>>> diff --git a/console.c b/console.c
>>>> index 4525cc7..9df1701 100644
>>>> --- a/console.c
>>>> +++ b/console.c
>>>> @@ -1612,7 +1612,7 @@ PixelFormat
>>>> qemu_different_endianness_pixelformat(int bpp)
>>>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>>>
>>>>       pf.bits_per_pixel = bpp;
>>>> -    pf.bytes_per_pixel = bpp / 8;
>>>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>>>       pf.depth = bpp == 32 ? 24 : bpp;
>>>>
>>>>       switch (bpp) {
>>>> @@ -1661,13 +1661,12 @@ PixelFormat qemu_default_pixelformat(int bpp)
>>>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>>>
>>>>       pf.bits_per_pixel = bpp;
>>>> -    pf.bytes_per_pixel = bpp / 8;
>>>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>>>       pf.depth = bpp == 32 ? 24 : bpp;
>>>>
>>>>       switch (bpp) {
>>>>           case 15:
>>>>               pf.bits_per_pixel = 16;
>>>> -            pf.bytes_per_pixel = 2;
>>> Removed unintentionally?
>>>
>>> Jan
>>
>> 15 bpp no longer needs special handling because
>> the computation above is fixed by the same patch,
>> so the removal is correct.
> 
> Ok, actually starting to look at this code: This is apparently a code
> cleanup, not a bug fix like the subject suggests. No valid input for
> could have actually triggered the round-up issue. Please declare it as
> such. Bonus for abort() on the invalid default cases.

Well, do not abort on bpp == 0, the curses case.

Also, qemu_different_endianness_pixelformat is currently only called
with 16 or 32 bpp (see vga.c), but only handles 24 and 32. Fishy...

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux

Re: [Qemu-devel] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Stefan Hajnoczi]

On Wed, Aug 22, 2012 at 05:19:42PM +0200, BALATON Zoltan wrote:
> Division with round up is the correct way to compute this even if the
> only case where division with round down gives incorrect result is
> probably 15 bpp. This case was explicitely patched up in one of these
> functions but was unhandled in the other. (I'm not sure about setting
> 16 bpp for the 15bpp case either but I left that there for now.)
> 
> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> ---
>  console.c |    5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
>  v2: Use DIV_ROUND_UP and extended commit message

Thanks, applied to the trivial patches tree:
https://github.com/stefanha/qemu/commits/trivial-patches

Stefan

Re: [Qemu-devel] [Qemu-trivial] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Stefan Hajnoczi]

On Wed, Aug 22, 2012 at 06:44:08PM +0200, Jan Kiszka wrote:
> On 2012-08-22 18:29, Stefan Weil wrote:
> > Am 22.08.2012 17:32, schrieb Jan Kiszka:
> >> On 2012-08-22 17:19, BALATON Zoltan wrote:
> >>> Division with round up is the correct way to compute this even if the
> >>> only case where division with round down gives incorrect result is
> >>> probably 15 bpp. This case was explicitely patched up in one of these
> >>> functions but was unhandled in the other. (I'm not sure about setting
> >>> 16 bpp for the 15bpp case either but I left that there for now.)
> >>>
> >>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> >>> ---
> >>>   console.c |    5 ++---
> >>>   1 file changed, 2 insertions(+), 3 deletions(-)
> >>>
> >>>   v2: Use DIV_ROUND_UP and extended commit message
> >>>
> >>> diff --git a/console.c b/console.c
> >>> index 4525cc7..9df1701 100644
> >>> --- a/console.c
> >>> +++ b/console.c
> >>> @@ -1612,7 +1612,7 @@ PixelFormat
> >>> qemu_different_endianness_pixelformat(int bpp)
> >>>       memset(&pf, 0x00, sizeof(PixelFormat));
> >>>
> >>>       pf.bits_per_pixel = bpp;
> >>> -    pf.bytes_per_pixel = bpp / 8;
> >>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
> >>>       pf.depth = bpp == 32 ? 24 : bpp;
> >>>
> >>>       switch (bpp) {
> >>> @@ -1661,13 +1661,12 @@ PixelFormat qemu_default_pixelformat(int bpp)
> >>>       memset(&pf, 0x00, sizeof(PixelFormat));
> >>>
> >>>       pf.bits_per_pixel = bpp;
> >>> -    pf.bytes_per_pixel = bpp / 8;
> >>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
> >>>       pf.depth = bpp == 32 ? 24 : bpp;
> >>>
> >>>       switch (bpp) {
> >>>           case 15:
> >>>               pf.bits_per_pixel = 16;
> >>> -            pf.bytes_per_pixel = 2;
> >> Removed unintentionally?
> >>
> >> Jan
> > 
> > 15 bpp no longer needs special handling because
> > the computation above is fixed by the same patch,
> > so the removal is correct.
> 
> Ok, actually starting to look at this code: This is apparently a code
> cleanup, not a bug fix like the subject suggests. No valid input for
> could have actually triggered the round-up issue. Please declare it as
> such. Bonus for abort() on the invalid default cases.

I have updated the commit message to "console: Clean up bytes per pixel
calculation".

Stefan

Re: [Qemu-devel] [Qemu-trivial] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Jan Kiszka]

On 2012-08-24 13:20, Stefan Hajnoczi wrote:
> On Wed, Aug 22, 2012 at 06:44:08PM +0200, Jan Kiszka wrote:
>> On 2012-08-22 18:29, Stefan Weil wrote:
>>> Am 22.08.2012 17:32, schrieb Jan Kiszka:
>>>> On 2012-08-22 17:19, BALATON Zoltan wrote:
>>>>> Division with round up is the correct way to compute this even if the
>>>>> only case where division with round down gives incorrect result is
>>>>> probably 15 bpp. This case was explicitely patched up in one of these
>>>>> functions but was unhandled in the other. (I'm not sure about setting
>>>>> 16 bpp for the 15bpp case either but I left that there for now.)
>>>>>
>>>>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
>>>>> ---
>>>>>   console.c |    5 ++---
>>>>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>>>>
>>>>>   v2: Use DIV_ROUND_UP and extended commit message
>>>>>
>>>>> diff --git a/console.c b/console.c
>>>>> index 4525cc7..9df1701 100644
>>>>> --- a/console.c
>>>>> +++ b/console.c
>>>>> @@ -1612,7 +1612,7 @@ PixelFormat
>>>>> qemu_different_endianness_pixelformat(int bpp)
>>>>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>>>>
>>>>>       pf.bits_per_pixel = bpp;
>>>>> -    pf.bytes_per_pixel = bpp / 8;
>>>>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>>>>       pf.depth = bpp == 32 ? 24 : bpp;
>>>>>
>>>>>       switch (bpp) {
>>>>> @@ -1661,13 +1661,12 @@ PixelFormat qemu_default_pixelformat(int bpp)
>>>>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>>>>
>>>>>       pf.bits_per_pixel = bpp;
>>>>> -    pf.bytes_per_pixel = bpp / 8;
>>>>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>>>>       pf.depth = bpp == 32 ? 24 : bpp;
>>>>>
>>>>>       switch (bpp) {
>>>>>           case 15:
>>>>>               pf.bits_per_pixel = 16;
>>>>> -            pf.bytes_per_pixel = 2;
>>>> Removed unintentionally?
>>>>
>>>> Jan
>>>
>>> 15 bpp no longer needs special handling because
>>> the computation above is fixed by the same patch,
>>> so the removal is correct.
>>
>> Ok, actually starting to look at this code: This is apparently a code
>> cleanup, not a bug fix like the subject suggests. No valid input for
>> could have actually triggered the round-up issue. Please declare it as
>> such. Bonus for abort() on the invalid default cases.
> 
> I have updated the commit message to "console: Clean up bytes per pixel
> calculation".

I think there was a v3 on the list, didn't check the details yet, though.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux

Re: [Qemu-devel] [Qemu-trivial] [PATCH v2] console: Correct computation of bytes per pixel from bits per pixel

[Stefan Hajnoczi]

On Fri, Aug 24, 2012 at 12:21 PM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
> On 2012-08-24 13:20, Stefan Hajnoczi wrote:
>> On Wed, Aug 22, 2012 at 06:44:08PM +0200, Jan Kiszka wrote:
>>> On 2012-08-22 18:29, Stefan Weil wrote:
>>>> Am 22.08.2012 17:32, schrieb Jan Kiszka:
>>>>> On 2012-08-22 17:19, BALATON Zoltan wrote:
>>>>>> Division with round up is the correct way to compute this even if the
>>>>>> only case where division with round down gives incorrect result is
>>>>>> probably 15 bpp. This case was explicitely patched up in one of these
>>>>>> functions but was unhandled in the other. (I'm not sure about setting
>>>>>> 16 bpp for the 15bpp case either but I left that there for now.)
>>>>>>
>>>>>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
>>>>>> ---
>>>>>>   console.c |    5 ++---
>>>>>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>>>>>
>>>>>>   v2: Use DIV_ROUND_UP and extended commit message
>>>>>>
>>>>>> diff --git a/console.c b/console.c
>>>>>> index 4525cc7..9df1701 100644
>>>>>> --- a/console.c
>>>>>> +++ b/console.c
>>>>>> @@ -1612,7 +1612,7 @@ PixelFormat
>>>>>> qemu_different_endianness_pixelformat(int bpp)
>>>>>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>>>>>
>>>>>>       pf.bits_per_pixel = bpp;
>>>>>> -    pf.bytes_per_pixel = bpp / 8;
>>>>>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>>>>>       pf.depth = bpp == 32 ? 24 : bpp;
>>>>>>
>>>>>>       switch (bpp) {
>>>>>> @@ -1661,13 +1661,12 @@ PixelFormat qemu_default_pixelformat(int bpp)
>>>>>>       memset(&pf, 0x00, sizeof(PixelFormat));
>>>>>>
>>>>>>       pf.bits_per_pixel = bpp;
>>>>>> -    pf.bytes_per_pixel = bpp / 8;
>>>>>> +    pf.bytes_per_pixel = DIV_ROUND_UP(bpp, 8);
>>>>>>       pf.depth = bpp == 32 ? 24 : bpp;
>>>>>>
>>>>>>       switch (bpp) {
>>>>>>           case 15:
>>>>>>               pf.bits_per_pixel = 16;
>>>>>> -            pf.bytes_per_pixel = 2;
>>>>> Removed unintentionally?
>>>>>
>>>>> Jan
>>>>
>>>> 15 bpp no longer needs special handling because
>>>> the computation above is fixed by the same patch,
>>>> so the removal is correct.
>>>
>>> Ok, actually starting to look at this code: This is apparently a code
>>> cleanup, not a bug fix like the subject suggests. No valid input for
>>> could have actually triggered the round-up issue. Please declare it as
>>> such. Bonus for abort() on the invalid default cases.
>>
>> I have updated the commit message to "console: Clean up bytes per pixel
>> calculation".
>
> I think there was a v3 on the list, didn't check the details yet, though.

Yes but it just adds more stuff that should be in separate patches.
Let's take v2 and additional changes can be done separately.

Stefan