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

From: Pekka Paalanen
Date: Mon Mar 25 2024 - 11:05:43 EST

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On Wed, 13 Mar 2024 18:44:58 +0100
Louis Chauvet <louis.chauvet@xxxxxxxxxxx> 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.

s/append/happen/

Reviewed-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx>

Thanks,
pq

>
> 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.
> + *
> + * @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.
> + *
> + * @in_pixel: Pointer to the pixel to read
> + * @out_pixel: Pointer to write the converted pixel
> + */
> +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
> + * 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,
>

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