Re: [PATCH v5 04/16] drm/vkms: Add typedef and documentation for pixel_read and pixel_write functions

From: Louis Chauvet
Date: Tue Mar 26 2024 - 11:57:21 EST

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In reply to: Maíra Canal: "Re: [PATCH v5 04/16] drm/vkms: Add typedef and documentation for pixel_read and pixel_write functions"
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Le 25/03/24 - 10:56, Maíra Canal a écrit :
> On 3/13/24 14:44, Louis Chauvet wrote:
> > Introduce two typedefs: pixel_read_t and pixel_write_t. It allows the
> > compiler to check if the passed functions take the correct arguments.
> > Such typedefs will help ensuring consistency across the code base in
> > case of update of these prototypes.
> >
> > Rename input/output variable in a consistent way between read_line and
> > write_line.
> >
> > A warn has been added in get_pixel_*_function to alert when an unsupported
> > pixel format is requested. As those formats are checked before
> > atomic_update callbacks, it should never append.
> >
> > Document for those typedefs.
> >
> > Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/vkms/vkms_drv.h | 23 ++++++-
> > drivers/gpu/drm/vkms/vkms_formats.c | 124 +++++++++++++++++++++---------------
> > drivers/gpu/drm/vkms/vkms_formats.h | 4 +-
> > drivers/gpu/drm/vkms/vkms_plane.c | 2 +-
> > 4 files changed, 95 insertions(+), 58 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > index 18086423a3a7..4bfc62d26f08 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > @@ -53,12 +53,31 @@ struct line_buffer {
> > struct pixel_argb_u16 *pixels;
> > };
> >
> > +/**
> > + * typedef pixel_write_t - These functions are used to read a pixel from a
> > + * `struct pixel_argb_u16*`, convert it in a specific format and write it in the @dst_pixels
> > + * buffer.
>
> Your brief description looks a bit big to me. Also, take a look at the
> cross-references docs [1].

Is this description sufficient?

typedef pixel_write_t - Convert a pixel from a &struct pixel_argb_u16 into a specific format

> [1]
> https://docs.kernel.org/doc-guide/kernel-doc.html#highlights-and-cross-references
>
> > + *
> > + * @out_pixel: destination address to write the pixel
> > + * @in_pixel: pixel to write
> > + */
> > +typedef void (*pixel_write_t)(u8 *out_pixel, struct pixel_argb_u16 *in_pixel);
> > +
> > struct vkms_writeback_job {
> > struct iosys_map data[DRM_FORMAT_MAX_PLANES];
> > struct vkms_frame_info wb_frame_info;
> > - void (*pixel_write)(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel);
> > + pixel_write_t pixel_write;
> > };
> >
> > +/**
> > + * typedef pixel_read_t - These functions are used to read a pixel in the source frame,
> > + * convert it to `struct pixel_argb_u16` and write it to @out_pixel.
>
> Same.

typedef pixel_read_t - Read a pixel and convert it to a &struct pixel_argb_u16

> > + *
> > + * @in_pixel: Pointer to the pixel to read
> > + * @out_pixel: Pointer to write the converted pixel
>
> s/Pointer/pointer

Fixed in v6.

> > + */
> > +typedef void (*pixel_read_t)(u8 *in_pixel, struct pixel_argb_u16 *out_pixel);
> > +
> > /**
> > * vkms_plane_state - Driver specific plane state
> > * @base: base plane state
> > @@ -69,7 +88,7 @@ struct vkms_writeback_job {
> > struct vkms_plane_state {
> > struct drm_shadow_plane_state base;
> > struct vkms_frame_info *frame_info;
> > - void (*pixel_read)(u8 *src_buffer, struct pixel_argb_u16 *out_pixel);
> > + pixel_read_t pixel_read;
> > };
> >
> > struct vkms_plane {
> > diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
> > index 6e3dc8682ff9..55a4365d21a4 100644
> > --- a/drivers/gpu/drm/vkms/vkms_formats.c
> > +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> > @@ -76,7 +76,7 @@ static int get_x_position(const struct vkms_frame_info *frame_info, int limit, i
> > * They are used in the `vkms_compose_row` function to handle multiple formats.
> > */
> >
> > -static void ARGB8888_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
> > +static void ARGB8888_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > {
> > /*
> > * The 257 is the "conversion ratio". This number is obtained by the
> > @@ -84,48 +84,48 @@ static void ARGB8888_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixe
> > * the best color value in a pixel format with more possibilities.
> > * A similar idea applies to others RGB color conversions.
> > */
> > - out_pixel->a = (u16)src_pixels[3] * 257;
> > - out_pixel->r = (u16)src_pixels[2] * 257;
> > - out_pixel->g = (u16)src_pixels[1] * 257;
> > - out_pixel->b = (u16)src_pixels[0] * 257;
> > + out_pixel->a = (u16)in_pixel[3] * 257;
> > + out_pixel->r = (u16)in_pixel[2] * 257;
> > + out_pixel->g = (u16)in_pixel[1] * 257;
> > + out_pixel->b = (u16)in_pixel[0] * 257;
> > }
> >
> > -static void XRGB8888_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
> > +static void XRGB8888_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > {
> > out_pixel->a = (u16)0xffff;
> > - out_pixel->r = (u16)src_pixels[2] * 257;
> > - out_pixel->g = (u16)src_pixels[1] * 257;
> > - out_pixel->b = (u16)src_pixels[0] * 257;
> > + out_pixel->r = (u16)in_pixel[2] * 257;
> > + out_pixel->g = (u16)in_pixel[1] * 257;
> > + out_pixel->b = (u16)in_pixel[0] * 257;
> > }
> >
> > -static void ARGB16161616_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
> > +static void ARGB16161616_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > {
> > - u16 *pixels = (u16 *)src_pixels;
> > + u16 *pixel = (u16 *)in_pixel;
> >
> > - out_pixel->a = le16_to_cpu(pixels[3]);
> > - out_pixel->r = le16_to_cpu(pixels[2]);
> > - out_pixel->g = le16_to_cpu(pixels[1]);
> > - out_pixel->b = le16_to_cpu(pixels[0]);
> > + out_pixel->a = le16_to_cpu(pixel[3]);
> > + out_pixel->r = le16_to_cpu(pixel[2]);
> > + out_pixel->g = le16_to_cpu(pixel[1]);
> > + out_pixel->b = le16_to_cpu(pixel[0]);
> > }
> >
> > -static void XRGB16161616_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
> > +static void XRGB16161616_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > {
> > - u16 *pixels = (u16 *)src_pixels;
> > + u16 *pixel = (u16 *)in_pixel;
> >
> > out_pixel->a = (u16)0xffff;
> > - out_pixel->r = le16_to_cpu(pixels[2]);
> > - out_pixel->g = le16_to_cpu(pixels[1]);
> > - out_pixel->b = le16_to_cpu(pixels[0]);
> > + out_pixel->r = le16_to_cpu(pixel[2]);
> > + out_pixel->g = le16_to_cpu(pixel[1]);
> > + out_pixel->b = le16_to_cpu(pixel[0]);
> > }
> >
> > -static void RGB565_to_argb_u16(u8 *src_pixels, struct pixel_argb_u16 *out_pixel)
> > +static void RGB565_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> > {
> > - u16 *pixels = (u16 *)src_pixels;
> > + u16 *pixel = (u16 *)in_pixel;
> >
> > s64 fp_rb_ratio = drm_fixp_div(drm_int2fixp(65535), drm_int2fixp(31));
> > s64 fp_g_ratio = drm_fixp_div(drm_int2fixp(65535), drm_int2fixp(63));
> >
> > - u16 rgb_565 = le16_to_cpu(*pixels);
> > + u16 rgb_565 = le16_to_cpu(*pixel);
> > s64 fp_r = drm_int2fixp((rgb_565 >> 11) & 0x1f);
> > s64 fp_g = drm_int2fixp((rgb_565 >> 5) & 0x3f);
> > s64 fp_b = drm_int2fixp(rgb_565 & 0x1f);
> > @@ -169,12 +169,12 @@ void vkms_compose_row(struct line_buffer *stage_buffer, struct vkms_plane_state
> >
> > /*
> > * The following functions take one argb_u16 pixel and convert it to a specific format. The
> > - * result is stored in @dst_pixels.
> > + * result is stored in @out_pixel.
> > *
> > * They are used in the `vkms_writeback_row` to convert and store a pixel from the src_buffer to
> > * the writeback buffer.
> > */
> > -static void argb_u16_to_ARGB8888(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
> > +static void argb_u16_to_ARGB8888(u8 *out_pixel, struct pixel_argb_u16 *in_pixel)
> > {
> > /*
> > * This sequence below is important because the format's byte order is
> > @@ -186,43 +186,43 @@ static void argb_u16_to_ARGB8888(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel
> > * | Addr + 2 | = Red channel
> > * | Addr + 3 | = Alpha channel
> > */
> > - dst_pixels[3] = DIV_ROUND_CLOSEST(in_pixel->a, 257);
> > - dst_pixels[2] = DIV_ROUND_CLOSEST(in_pixel->r, 257);
> > - dst_pixels[1] = DIV_ROUND_CLOSEST(in_pixel->g, 257);
> > - dst_pixels[0] = DIV_ROUND_CLOSEST(in_pixel->b, 257);
> > + out_pixel[3] = DIV_ROUND_CLOSEST(in_pixel->a, 257);
> > + out_pixel[2] = DIV_ROUND_CLOSEST(in_pixel->r, 257);
> > + out_pixel[1] = DIV_ROUND_CLOSEST(in_pixel->g, 257);
> > + out_pixel[0] = DIV_ROUND_CLOSEST(in_pixel->b, 257);
> > }
> >
> > -static void argb_u16_to_XRGB8888(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
> > +static void argb_u16_to_XRGB8888(u8 *out_pixel, struct pixel_argb_u16 *in_pixel)
> > {
> > - dst_pixels[3] = 0xff;
> > - dst_pixels[2] = DIV_ROUND_CLOSEST(in_pixel->r, 257);
> > - dst_pixels[1] = DIV_ROUND_CLOSEST(in_pixel->g, 257);
> > - dst_pixels[0] = DIV_ROUND_CLOSEST(in_pixel->b, 257);
> > + out_pixel[3] = 0xff;
> > + out_pixel[2] = DIV_ROUND_CLOSEST(in_pixel->r, 257);
> > + out_pixel[1] = DIV_ROUND_CLOSEST(in_pixel->g, 257);
> > + out_pixel[0] = DIV_ROUND_CLOSEST(in_pixel->b, 257);
> > }
> >
> > -static void argb_u16_to_ARGB16161616(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
> > +static void argb_u16_to_ARGB16161616(u8 *out_pixel, struct pixel_argb_u16 *in_pixel)
> > {
> > - u16 *pixels = (u16 *)dst_pixels;
> > + u16 *pixel = (u16 *)out_pixel;
> >
> > - pixels[3] = cpu_to_le16(in_pixel->a);
> > - pixels[2] = cpu_to_le16(in_pixel->r);
> > - pixels[1] = cpu_to_le16(in_pixel->g);
> > - pixels[0] = cpu_to_le16(in_pixel->b);
> > + pixel[3] = cpu_to_le16(in_pixel->a);
> > + pixel[2] = cpu_to_le16(in_pixel->r);
> > + pixel[1] = cpu_to_le16(in_pixel->g);
> > + pixel[0] = cpu_to_le16(in_pixel->b);
> > }
> >
> > -static void argb_u16_to_XRGB16161616(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
> > +static void argb_u16_to_XRGB16161616(u8 *out_pixel, struct pixel_argb_u16 *in_pixel)
> > {
> > - u16 *pixels = (u16 *)dst_pixels;
> > + u16 *pixel = (u16 *)out_pixel;
> >
> > - pixels[3] = 0xffff;
> > - pixels[2] = cpu_to_le16(in_pixel->r);
> > - pixels[1] = cpu_to_le16(in_pixel->g);
> > - pixels[0] = cpu_to_le16(in_pixel->b);
> > + pixel[3] = 0xffff;
> > + pixel[2] = cpu_to_le16(in_pixel->r);
> > + pixel[1] = cpu_to_le16(in_pixel->g);
> > + pixel[0] = cpu_to_le16(in_pixel->b);
> > }
> >
> > -static void argb_u16_to_RGB565(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
> > +static void argb_u16_to_RGB565(u8 *out_pixel, struct pixel_argb_u16 *in_pixel)
> > {
> > - u16 *pixels = (u16 *)dst_pixels;
> > + u16 *pixel = (u16 *)out_pixel;
> >
> > s64 fp_rb_ratio = drm_fixp_div(drm_int2fixp(65535), drm_int2fixp(31));
> > s64 fp_g_ratio = drm_fixp_div(drm_int2fixp(65535), drm_int2fixp(63));
> > @@ -235,7 +235,7 @@ static void argb_u16_to_RGB565(u8 *dst_pixels, struct pixel_argb_u16 *in_pixel)
> > u16 g = drm_fixp2int(drm_fixp_div(fp_g, fp_g_ratio));
> > u16 b = drm_fixp2int(drm_fixp_div(fp_b, fp_rb_ratio));
> >
> > - *pixels = cpu_to_le16(r << 11 | g << 5 | b);
> > + *pixel = cpu_to_le16(r << 11 | g << 5 | b);
> > }
> >
> > /**
> > @@ -266,7 +266,7 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
> > *
> > * @format: DRM_FORMAT_* value for which to obtain a conversion function (see [drm_fourcc.h])
> > */
> > -void *get_pixel_conversion_function(u32 format)
> > +pixel_read_t get_pixel_read_function(u32 format)
> > {
> > switch (format) {
> > case DRM_FORMAT_ARGB8888:
> > @@ -280,7 +280,16 @@ void *get_pixel_conversion_function(u32 format)
> > case DRM_FORMAT_RGB565:
> > return &RGB565_to_argb_u16;
> > default:
> > - return NULL;
> > + /*
> > + * This is a bug in vkms_plane_atomic_check. All the supported
>
> s/vkms_plane_atomic_check/vkms_plane_atomic_check()

Fixed in v6.

Thanks,
Louis Chauvet

> Best Regards,
> - Maíra
>
> > + * format must:
> > + * - Be listed in vkms_formats in vkms_plane.c
> > + * - Have a pixel_read callback defined here
> > + */
> > + WARN(true,
> > + "Pixel format %p4cc is not supported by VKMS planes. This is a kernel bug, atomic check must forbid this configuration.\n",
> > + &format);
> > + return (pixel_read_t)NULL;
> > }
> > }
> >
> > @@ -291,7 +300,7 @@ void *get_pixel_conversion_function(u32 format)
> > *
> > * @format: DRM_FORMAT_* value for which to obtain a conversion function (see [drm_fourcc.h])
> > */
> > -void *get_pixel_write_function(u32 format)
> > +pixel_write_t get_pixel_write_function(u32 format)
> > {
> > switch (format) {
> > case DRM_FORMAT_ARGB8888:
> > @@ -305,6 +314,15 @@ void *get_pixel_write_function(u32 format)
> > case DRM_FORMAT_RGB565:
> > return &argb_u16_to_RGB565;
> > default:
> > - return NULL;
> > + /*
> > + * This is a bug in vkms_writeback_atomic_check. All the supported
> > + * format must:
> > + * - Be listed in vkms_wb_formats in vkms_writeback.c
> > + * - Have a pixel_write callback defined here
> > + */
> > + WARN(true,
> > + "Pixel format %p4cc is not supported by VKMS writeback. This is a kernel bug, atomic check must forbid this configuration.\n",
> > + &format);
> > + return (pixel_write_t)NULL;
> > }
> > }
> > diff --git a/drivers/gpu/drm/vkms/vkms_formats.h b/drivers/gpu/drm/vkms/vkms_formats.h
> > index cf59c2ed8e9a..3ecea4563254 100644
> > --- a/drivers/gpu/drm/vkms/vkms_formats.h
> > +++ b/drivers/gpu/drm/vkms/vkms_formats.h
> > @@ -5,8 +5,8 @@
> >
> > #include "vkms_drv.h"
> >
> > -void *get_pixel_conversion_function(u32 format);
> > +pixel_read_t get_pixel_read_function(u32 format);
> >
> > -void *get_pixel_write_function(u32 format);
> > +pixel_write_t get_pixel_write_function(u32 format);
> >
> > #endif /* _VKMS_FORMATS_H_ */
> > diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> > index 21b5adfb44aa..10e9b23dab28 100644
> > --- a/drivers/gpu/drm/vkms/vkms_plane.c
> > +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> > @@ -125,7 +125,7 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
> > drm_rect_rotate(&frame_info->rotated, drm_rect_width(&frame_info->rotated),
> > drm_rect_height(&frame_info->rotated), frame_info->rotation);
> >
> > - vkms_plane_state->pixel_read = get_pixel_conversion_function(fmt);
> > + vkms_plane_state->pixel_read = get_pixel_read_function(fmt);
> > }
> >
> > static int vkms_plane_atomic_check(struct drm_plane *plane,
> >

--
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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