[PATCH v11 0/1] [DRIVER] gpu: drm: add support for YHGCH ZX1000 soc chipset

[Chu Guangqing]

Hi Thomas,

The link to the new PR is here.

https://lore.kernel.org/all/20251202022452.2636-1-chuguangqing@xxxxxxxxxx/

> diff --git a/drivers/gpu/drm/yhgch/yhgch_drm_vdac.c b/drivers/gpu/drm/yhgch/yhgch_drm_vdac.c
> new file mode 100644
> index 000000000000..2de95c887b62
> --- /dev/null
> +++ b/drivers/gpu/drm/yhgch/yhgch_drm_vdac.c
> @@ -0,0 +1,137 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/io.h>
> +
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_edid.h>
> +#include <drm/drm_probe_helper.h>
> +#include <drm/drm_print.h>
> +#include <drm/drm_simple_kms_helper.h>
> +
> +#include "yhgch_drm_drv.h"
> +#include "yhgch_drm_regs.h"
> +
> +static int yhgch_connector_get_modes(struct drm_connector *connector)
> +{
> +	int count;
> +	const struct drm_edid *drm_edid;
> +
> +	drm_edid = drm_edid_read(connector);
> +	if (drm_edid) {
> +		drm_edid_connector_update(connector, drm_edid);
> +		count =  drm_edid_connector_add_modes(connector);
> +		drm_edid_free(drm_edid);
> +		if (count)
> +			goto out;

Don't do the goto here. Simple call drm_edid_free().

> +	} else {
> +		drm_edid_connector_update(connector, NULL);
> +	}
> +
> +	count = drm_add_modes_noedid(connector,
> +				     connector->dev->mode_config.max_width,
> +				     connector->dev->mode_config.max_height);
> +	drm_set_preferred_mode(connector, 1024, 768);

These two calls belong into the else branch. If you have an EDID, please 
don't try to make up your own defaults.

Answer: This is to avoid encountering the situation where the display cannot be
read (some special displays do not have EDID).

> +
> +out:
> +	drm_edid_free(drm_edid);

This only belongs into the if branch. You also have a double free on 
drm_edid in that case. I wonder how you did not notice.

Answer: Revisions have been made in accordance with your requirements. We
apologize for not noticing the double free issue and thank you for pointing it out.

> +	return count;

Returning 0 here is not a problem. DRM will try several steps to figure 
out the display modes, and eventually fallback to defaults.

Best regards

Chu Guangqing