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Date: Tue, 25 Aug 2020 12:42:46 -0300 From: Melissa Wen <melissa.srw@...il.com> To: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com> Cc: linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, Brian Starkey <brian.starkey@....com>, Liviu Dudau <liviu.dudau@....com>, Daniel Vetter <daniel@...ll.ch>, Simon Ser <contact@...rsion.fr>, Leandro Ribeiro <leandro.ribeiro@...labora.com>, daniels@...labora.com, Emil Velikov <emil.l.velikov@...il.com> Subject: Re: [PATCH v5 2/3] drm/vkms: Compute CRC without change input data On 08/24, Rodrigo Siqueira wrote: > The compute_crc() function is responsible for calculating the > framebuffer CRC value; due to the XRGB format, this function has to > ignore the alpha channel during the CRC computation. Therefore, > compute_crc() set zero to the alpha channel directly in the input > framebuffer, which is not a problem since this function receives a copy > of the original buffer. However, if we want to use this function in a > context without a buffer copy, it will change the initial value. This > patch makes compute_crc() calculate the CRC value without modifying the > input framebuffer. > > Change in V4 (Emil): > - Move bitmap_clear operation and comments to get_pixel function > > Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@...il.com> > --- > drivers/gpu/drm/vkms/vkms_composer.c | 38 ++++++++++++++++++---------- > 1 file changed, 24 insertions(+), 14 deletions(-) > > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c > index 4d8bc04bb6ee..387b0690a64a 100644 > --- a/drivers/gpu/drm/vkms/vkms_composer.c > +++ b/drivers/gpu/drm/vkms/vkms_composer.c > @@ -9,33 +9,43 @@ > > #include "vkms_drv.h" > > +static u32 get_pixel_from_buffer(int x, int y, const u8 *buffer, > + const struct vkms_composer *composer) > +{ > + u32 pixel; > + int src_offset = composer->offset + (y * composer->pitch) > + + (x * composer->cpp); > + > + pixel = *(u32 *)&buffer[src_offset]; > + /* XRGB format ignores Alpha channel */ > + bitmap_clear((void *)&pixel, 0, 8); I noticed a small problem in this bitmap_clear as I recently sent a patch changing it. The starting point for zeroing the alpha is not 0, but 24. As in the removed line below: - bitmap_clear(vaddr_out + src_offset, 24, 8); It affects the kms_cursor_crc/cursor-alpha-transparent subtest. > + > + return pixel; > +} > + > /** > * compute_crc - Compute CRC value on output frame > * > - * @vaddr_out: address to final framebuffer > + * @vaddr: address to final framebuffer > * @composer: framebuffer's metadata > * > * returns CRC value computed using crc32 on the visible portion of > * the final framebuffer at vaddr_out > */ > -static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer) > +static uint32_t compute_crc(const u8 *vaddr, > + const struct vkms_composer *composer) > { > - int i, j, src_offset; > + int x, y; > + u32 crc = 0, pixel = 0; > int x_src = composer->src.x1 >> 16; > int y_src = composer->src.y1 >> 16; > int h_src = drm_rect_height(&composer->src) >> 16; > int w_src = drm_rect_width(&composer->src) >> 16; > - u32 crc = 0; > - > - for (i = y_src; i < y_src + h_src; ++i) { > - for (j = x_src; j < x_src + w_src; ++j) { > - src_offset = composer->offset > - + (i * composer->pitch) > - + (j * composer->cpp); > - /* XRGB format ignores Alpha channel */ > - bitmap_clear(vaddr_out + src_offset, 24, 8); > - crc = crc32_le(crc, vaddr_out + src_offset, > - sizeof(u32)); > + > + for (y = y_src; y < y_src + h_src; ++y) { > + for (x = x_src; x < x_src + w_src; ++x) { > + pixel = get_pixel_from_buffer(x, y, vaddr, composer); > + crc = crc32_le(crc, (void *)&pixel, sizeof(u32)); > } > } > > -- > 2.28.0 >
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