| Message ID | 5bbc05f52d23b17cc0faa81a2e5d4f2a344aaaa9.1409841955.git.m.chehab@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
I need to review this more closely tomorrow. Hans On 09/04/14 16:46, Mauro Carvalho Chehab wrote: > This code implicitly assumes that pagesize is 4096, but this is > not true on all archs, as the PAGE_SHIFT can be different than > 12 on all those architectures: alpha, arc, arm64, cris, frv, > hexagon,ia64, m68k, metag, microblaze, mips, openrisc, parisc, > powerpc, sh, sparc and tile. > > The real constrant here seems to be to limit the buffer size to > 4MB. > > So, fix the code to reflect that, in a way that it will keep > working with differnt values for PAGE_SIZE. > > Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com> > > diff --git a/drivers/media/pci/tw68/tw68-video.c b/drivers/media/pci/tw68/tw68-video.c > index 4dd38578cf1b..66658accdca9 100644 > --- a/drivers/media/pci/tw68/tw68-video.c > +++ b/drivers/media/pci/tw68/tw68-video.c > @@ -366,7 +366,7 @@ static int tw68_buffer_pages(int size) > { > size = PAGE_ALIGN(size); > size += PAGE_SIZE; /* for non-page-aligned buffers */ > - size /= 4096; > + size /= PAGE_SIZE; > return size; > } > > @@ -376,7 +376,7 @@ static int tw68_buffer_count(unsigned int size, unsigned int count) > { > unsigned int maxcount; > > - maxcount = 1024 / tw68_buffer_pages(size); > + maxcount = (4096 * 1024 / PAGE_SIZE) / tw68_buffer_pages(size); > if (count > maxcount) > count = maxcount; > return count; > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 09/04/2014 04:46 PM, Mauro Carvalho Chehab wrote: > This code implicitly assumes that pagesize is 4096, but this is > not true on all archs, as the PAGE_SHIFT can be different than > 12 on all those architectures: alpha, arc, arm64, cris, frv, > hexagon,ia64, m68k, metag, microblaze, mips, openrisc, parisc, > powerpc, sh, sparc and tile. > > The real constrant here seems to be to limit the buffer size to > 4MB. > > So, fix the code to reflect that, in a way that it will keep > working with differnt values for PAGE_SIZE. While your fix is OK, I have a better patch that makes the code a lot more readable. I'll post that soon. Regards, Hans > > Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com> > > diff --git a/drivers/media/pci/tw68/tw68-video.c b/drivers/media/pci/tw68/tw68-video.c > index 4dd38578cf1b..66658accdca9 100644 > --- a/drivers/media/pci/tw68/tw68-video.c > +++ b/drivers/media/pci/tw68/tw68-video.c > @@ -366,7 +366,7 @@ static int tw68_buffer_pages(int size) > { > size = PAGE_ALIGN(size); > size += PAGE_SIZE; /* for non-page-aligned buffers */ > - size /= 4096; > + size /= PAGE_SIZE; > return size; > } > > @@ -376,7 +376,7 @@ static int tw68_buffer_count(unsigned int size, unsigned int count) > { > unsigned int maxcount; > > - maxcount = 1024 / tw68_buffer_pages(size); > + maxcount = (4096 * 1024 / PAGE_SIZE) / tw68_buffer_pages(size); > if (count > maxcount) > count = maxcount; > return count; > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/media/pci/tw68/tw68-video.c b/drivers/media/pci/tw68/tw68-video.c index 4dd38578cf1b..66658accdca9 100644 --- a/drivers/media/pci/tw68/tw68-video.c +++ b/drivers/media/pci/tw68/tw68-video.c @@ -366,7 +366,7 @@ static int tw68_buffer_pages(int size) { size = PAGE_ALIGN(size); size += PAGE_SIZE; /* for non-page-aligned buffers */ - size /= 4096; + size /= PAGE_SIZE; return size; } @@ -376,7 +376,7 @@ static int tw68_buffer_count(unsigned int size, unsigned int count) { unsigned int maxcount; - maxcount = 1024 / tw68_buffer_pages(size); + maxcount = (4096 * 1024 / PAGE_SIZE) / tw68_buffer_pages(size); if (count > maxcount) count = maxcount; return count;
This code implicitly assumes that pagesize is 4096, but this is not true on all archs, as the PAGE_SHIFT can be different than 12 on all those architectures: alpha, arc, arm64, cris, frv, hexagon,ia64, m68k, metag, microblaze, mips, openrisc, parisc, powerpc, sh, sparc and tile. The real constrant here seems to be to limit the buffer size to 4MB. So, fix the code to reflect that, in a way that it will keep working with differnt values for PAGE_SIZE. Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>