[PATCH 7/7] drm/gud: Add module parameter to control emulation: xrgb8888

[Noralf Trønnes]

For devices that don't support XRGB8888 give the user the ability to
choose what's most important: Color depth or frames per second.

Add an 'xrgb8888' module parameter to override the emulation format.

Assume the user wants full control if xrgb8888 is set and don't set
DRM_CAP_DUMB_PREFERRED_DEPTH if RGB565 is supported (AFAIK only X.org
supports this).

Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
---
 drivers/gpu/drm/gud/gud_drv.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/gud/gud_drv.c b/drivers/gpu/drm/gud/gud_drv.c
index 3f9d4b9a1e3d..60d27ee5ddbd 100644
--- a/drivers/gpu/drm/gud/gud_drv.c
+++ b/drivers/gpu/drm/gud/gud_drv.c
@@ -30,6 +30,10 @@
 
 #include "gud_internal.h"
 
+static int gud_xrgb8888;
+module_param_named(xrgb8888, gud_xrgb8888, int, 0644);
+MODULE_PARM_DESC(xrgb8888, "XRGB8888 emulation format: GUD_PIXEL_FORMAT_* value, 0=auto, -1=disable [default=auto]");
+
 /* Only used internally */
 static const struct drm_format_info gud_drm_format_r1 = {
 	.format = GUD_DRM_FORMAT_R1,
@@ -530,12 +534,12 @@ static int gud_probe(struct usb_interface *intf, const struct usb_device_id *id)
 		case DRM_FORMAT_RGB332:
 			fallthrough;
 		case DRM_FORMAT_RGB888:
-			if (!xrgb8888_emulation_format)
+			if (!gud_xrgb8888 && !xrgb8888_emulation_format)
 				xrgb8888_emulation_format = info;
 			break;
 		case DRM_FORMAT_RGB565:
 			rgb565_supported = true;
-			if (!xrgb8888_emulation_format)
+			if (!gud_xrgb8888 && !xrgb8888_emulation_format)
 				xrgb8888_emulation_format = info;
 			break;
 		case DRM_FORMAT_XRGB8888:
@@ -543,6 +547,9 @@ static int gud_probe(struct usb_interface *intf, const struct usb_device_id *id)
 			break;
 		}
 
+		if (gud_xrgb8888 == formats_dev[i])
+			xrgb8888_emulation_format = info;
+
 		fmt_buf_size = drm_format_info_min_pitch(info, 0, drm->mode_config.max_width) *
 			       drm->mode_config.max_height;
 		max_buffer_size = max(max_buffer_size, fmt_buf_size);
@@ -559,7 +566,7 @@ static int gud_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	}
 
 	/* Prefer speed over color depth */
-	if (rgb565_supported)
+	if (!gud_xrgb8888 && rgb565_supported)
 		drm->mode_config.preferred_depth = 16;
 
 	if (!xrgb8888_supported && xrgb8888_emulation_format) {
-- 
2.32.0