On 12/19/25 15:55, Luca Ceresoli wrote:
Hi Louis,
On Wed Oct 29, 2025 at 3:36 PM CET, Louis Chauvet wrote:
VKMS driver supports all the pixel formats for planes, but for testing it
can be useful to only advertise few of them. This new configuration
interface will allow configuring the pixel format per planes.
[...]
Signed-off-by: Louis Chauvet <[email protected]>
+int __must_check vkms_config_plane_add_format(struct vkms_config_plane
*plane_cfg, u32 drm_format)
+{
+ bool found = false;
+
+ for (int i = 0; i < ARRAY_SIZE(vkms_supported_plane_formats); i++) {
+ if (vkms_supported_plane_formats[i] == drm_format) {
+ found = true;
+ break;
+ }
+ }
+
+ if (!found)
+ return -EINVAL;
+ for (unsigned int i = 0; i < plane_cfg->supported_formats_count; i++) {
+ if (plane_cfg->supported_formats[i] == drm_format)
+ return 0;
+ }
+ u32 *new_ptr = krealloc_array(plane_cfg->supported_formats,
+ plane_cfg->supported_formats_count + 1,
+ sizeof(*plane_cfg->supported_formats),
GFP_KERNEL);
+ if (!new_ptr)
+ return -ENOMEM;
+
+ plane_cfg->supported_formats = new_ptr;
+ plane_cfg->supported_formats[plane_cfg->supported_formats_count] =
drm_format;
+ plane_cfg->supported_formats_count++;
+
+ return 0;
+}
This whole logic appears quite complex for what you need here. I suspect
using the facilities in linux/bitmap.h would make your code simpler by
allocating a (multi-)ulong array of
ARRAY_SIZE(vkms_supported_plane_formats) bits. This would surely use less
memory and avoid all reallocations, too.
I agree this look complex, but I need an array anyway to interface with
DRM core. If I use a bitmap, I would have to manage a mapping bit <=>
fourcc value, which would not be really simpler I think.
I will simplify it a little bit by extracting some helpers for v2:
int __must_check vkms_config_plane_add_format(struct vkms_config_plane
*plane_cfg, u32 drm_format) {
if (!supported_format(drm_format))
return -EINVAL;
if (already_present(drm_format))
return 0;
new_ptr = krealloc
[...]
}
If this is not sufficient, I will take a look at bitfield next year.
--- a/drivers/gpu/drm/vkms/vkms_config.h
+++ b/drivers/gpu/drm/vkms/vkms_config.h
+/**
+ * vkms_config_plane_remove_format - Remove a specific format from a plane
+ * @plane_cfg: Plane to remove the format to
+ * @drm_format: Format to remove
+ */
+void vkms_config_plane_remove_format(struct vkms_config_plane *plane_cfg, u32
drm_format);
+
+/**
+ * vkms_config_plane_remove_all_formats - Remove all formast from a plane
formats
Luca
--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
