Re: [PATCH 05/39] drm/imx: dc: Rework dc_subdev_get_id() to drop ARRAY_SIZE() use

[Frank Li <Frank.li@nxp.com>]

On Sat, Oct 11, 2025 at 06:51:20PM +0200, Marek Vasut wrote:
> Rework dc_subdev_get_id() to drop ARRAY_SIZE() use and use empty trailing
> entry in each ID look up array instead. This allows passing of those arrays
> around as OF match data, which will be useful when using this pipeline on
> i.MX95, which has different address-to-ID mapping.
>
> Signed-off-by: Marek Vasut <marek.vasut@mailbox.org>

This change is okay. but my questions is why need map register to id.

Frank

> ---
> Cc: Abel Vesa <abelvesa@kernel.org>
> Cc: Conor Dooley <conor+dt@kernel.org>
> Cc: Fabio Estevam <festevam@gmail.com>
> Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
> Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> Cc: Liu Ying <victor.liu@nxp.com>
> Cc: Lucas Stach <l.stach@pengutronix.de>
> Cc: Peng Fan <peng.fan@nxp.com>
> Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: devicetree@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Cc: imx@lists.linux.dev
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-clk@vger.kernel.org
> ---
>  drivers/gpu/drm/imx/dc/dc-cf.c  | 3 ++-
>  drivers/gpu/drm/imx/dc/dc-db.c  | 3 ++-
>  drivers/gpu/drm/imx/dc/dc-de.c  | 3 ++-
>  drivers/gpu/drm/imx/dc/dc-drv.h | 8 +++++---
>  drivers/gpu/drm/imx/dc/dc-ed.c  | 3 ++-
>  drivers/gpu/drm/imx/dc/dc-fg.c  | 3 ++-
>  drivers/gpu/drm/imx/dc/dc-fl.c  | 3 ++-
>  drivers/gpu/drm/imx/dc/dc-fw.c  | 3 ++-
>  drivers/gpu/drm/imx/dc/dc-lb.c  | 3 ++-
>  drivers/gpu/drm/imx/dc/dc-tc.c  | 3 ++-
>  10 files changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/imx/dc/dc-cf.c b/drivers/gpu/drm/imx/dc/dc-cf.c
> index 2f077161e9126..846705534546a 100644
> --- a/drivers/gpu/drm/imx/dc/dc-cf.c
> +++ b/drivers/gpu/drm/imx/dc/dc-cf.c
> @@ -29,6 +29,7 @@ static const struct dc_subdev_info dc_cf_info[] = {
>  	{ .reg_start = 0x561809e0, .id = 1, },
>  	{ .reg_start = 0x561809a0, .id = 4, },
>  	{ .reg_start = 0x56180a20, .id = 5, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_cf_regmap_ranges[] = {
> @@ -106,7 +107,7 @@ static int dc_cf_bind(struct device *dev, struct device *master, void *data)
>  	if (IS_ERR(cf->reg_cfg))
>  		return PTR_ERR(cf->reg_cfg);
>
> -	id = dc_subdev_get_id(dc_cf_info, ARRAY_SIZE(dc_cf_info), res_pec);
> +	id = dc_subdev_get_id(dc_cf_info, res_pec);
>  	if (id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", id);
>  		return id;
> diff --git a/drivers/gpu/drm/imx/dc/dc-db.c b/drivers/gpu/drm/imx/dc/dc-db.c
> index 789942d1c446d..3958a2c4ec934 100644
> --- a/drivers/gpu/drm/imx/dc/dc-db.c
> +++ b/drivers/gpu/drm/imx/dc/dc-db.c
> @@ -74,6 +74,7 @@ enum dc_db_shadow_sel {
>  static const struct dc_subdev_info dc_db_info[] = {
>  	{ .reg_start = 0x4b6a0000, .id = 0, },
>  	{ .reg_start = 0x4b720000, .id = 1, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_db_regmap_ranges[] = {
> @@ -176,7 +177,7 @@ static int dc_db_bind(struct device *dev, struct device *master, void *data)
>  	if (IS_ERR(db->reg_cfg))
>  		return PTR_ERR(db->reg_cfg);
>
> -	db->id = dc_subdev_get_id(dc_db_info, ARRAY_SIZE(dc_db_info), res_cfg);
> +	db->id = dc_subdev_get_id(dc_db_info, res_cfg);
>  	if (db->id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", db->id);
>  		return db->id;
> diff --git a/drivers/gpu/drm/imx/dc/dc-de.c b/drivers/gpu/drm/imx/dc/dc-de.c
> index 23b0cea68d325..81334c0088219 100644
> --- a/drivers/gpu/drm/imx/dc/dc-de.c
> +++ b/drivers/gpu/drm/imx/dc/dc-de.c
> @@ -21,6 +21,7 @@
>  static const struct dc_subdev_info dc_de_info[] = {
>  	{ .reg_start = 0x5618b400, .id = 0, },
>  	{ .reg_start = 0x5618b420, .id = 1, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_de_regmap_ranges[] = {
> @@ -90,7 +91,7 @@ static int dc_de_bind(struct device *dev, struct device *master, void *data)
>  	if (ret)
>  		return ret;
>
> -	id = dc_subdev_get_id(dc_de_info, ARRAY_SIZE(dc_de_info), res_top);
> +	id = dc_subdev_get_id(dc_de_info, res_top);
>  	if (id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", id);
>  		return id;
> diff --git a/drivers/gpu/drm/imx/dc/dc-drv.h b/drivers/gpu/drm/imx/dc/dc-drv.h
> index 17ce2d748262b..a7ad17680a9b2 100644
> --- a/drivers/gpu/drm/imx/dc/dc-drv.h
> +++ b/drivers/gpu/drm/imx/dc/dc-drv.h
> @@ -85,16 +85,18 @@ extern struct platform_driver dc_pe_driver;
>  extern struct platform_driver dc_tc_driver;
>
>  static inline int dc_subdev_get_id(const struct dc_subdev_info *info,
> -				   int info_cnt, struct resource *res)
> +				   struct resource *res)
>  {
> -	int i;
> +	int i = 0;
>
>  	if (!res)
>  		return -EINVAL;
>
> -	for (i = 0; i < info_cnt; i++)
> +	while (info[i].reg_start) {
>  		if (info[i].reg_start == res->start)
>  			return info[i].id;
> +		i++;
> +	}
>
>  	return -EINVAL;
>  }
> diff --git a/drivers/gpu/drm/imx/dc/dc-ed.c b/drivers/gpu/drm/imx/dc/dc-ed.c
> index 86ecc22d0a554..a63c387a4c023 100644
> --- a/drivers/gpu/drm/imx/dc/dc-ed.c
> +++ b/drivers/gpu/drm/imx/dc/dc-ed.c
> @@ -40,6 +40,7 @@ static const struct dc_subdev_info dc_ed_info[] = {
>  	{ .reg_start = 0x56180a00, .id = 1, },
>  	{ .reg_start = 0x561809c0, .id = 4, },
>  	{ .reg_start = 0x56180a40, .id = 5, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_ed_pec_regmap_write_ranges[] = {
> @@ -226,7 +227,7 @@ static int dc_ed_bind(struct device *dev, struct device *master, void *data)
>
>  	ed->dev = dev;
>
> -	id = dc_subdev_get_id(dc_ed_info, ARRAY_SIZE(dc_ed_info), res_pec);
> +	id = dc_subdev_get_id(dc_ed_info, res_pec);
>  	if (id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", id);
>  		return id;
> diff --git a/drivers/gpu/drm/imx/dc/dc-fg.c b/drivers/gpu/drm/imx/dc/dc-fg.c
> index 7f6c1852bf724..5fadd67aa911b 100644
> --- a/drivers/gpu/drm/imx/dc/dc-fg.c
> +++ b/drivers/gpu/drm/imx/dc/dc-fg.c
> @@ -92,6 +92,7 @@ enum dc_fg_dm {
>  static const struct dc_subdev_info dc_fg_info[] = {
>  	{ .reg_start = 0x5618b800, .id = 0, },
>  	{ .reg_start = 0x5618d400, .id = 1, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_fg_regmap_write_ranges[] = {
> @@ -326,7 +327,7 @@ static int dc_fg_bind(struct device *dev, struct device *master, void *data)
>  		return dev_err_probe(dev, PTR_ERR(fg->clk_disp),
>  				     "failed to get display clock\n");
>
> -	id = dc_subdev_get_id(dc_fg_info, ARRAY_SIZE(dc_fg_info), res);
> +	id = dc_subdev_get_id(dc_fg_info, res);
>  	if (id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", id);
>  		return id;
> diff --git a/drivers/gpu/drm/imx/dc/dc-fl.c b/drivers/gpu/drm/imx/dc/dc-fl.c
> index 3ce24c72aa13e..d4e746f8c4297 100644
> --- a/drivers/gpu/drm/imx/dc/dc-fl.c
> +++ b/drivers/gpu/drm/imx/dc/dc-fl.c
> @@ -33,6 +33,7 @@ struct dc_fl {
>
>  static const struct dc_subdev_info dc_fl_info[] = {
>  	{ .reg_start = 0x56180ac0, .id = 0, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_fl_regmap_ranges[] = {
> @@ -120,7 +121,7 @@ static int dc_fl_bind(struct device *dev, struct device *master, void *data)
>  	if (IS_ERR(fu->reg_cfg))
>  		return PTR_ERR(fu->reg_cfg);
>
> -	id = dc_subdev_get_id(dc_fl_info, ARRAY_SIZE(dc_fl_info), res_pec);
> +	id = dc_subdev_get_id(dc_fl_info, res_pec);
>  	if (id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", id);
>  		return id;
> diff --git a/drivers/gpu/drm/imx/dc/dc-fw.c b/drivers/gpu/drm/imx/dc/dc-fw.c
> index acb2d4d9e2ecd..c1131b7b17c2f 100644
> --- a/drivers/gpu/drm/imx/dc/dc-fw.c
> +++ b/drivers/gpu/drm/imx/dc/dc-fw.c
> @@ -35,6 +35,7 @@ struct dc_fw {
>
>  static const struct dc_subdev_info dc_fw_info[] = {
>  	{ .reg_start = 0x56180a60, .id = 2, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_fw_pec_regmap_access_ranges[] = {
> @@ -157,7 +158,7 @@ static int dc_fw_bind(struct device *dev, struct device *master, void *data)
>  	if (IS_ERR(fu->reg_cfg))
>  		return PTR_ERR(fu->reg_cfg);
>
> -	id = dc_subdev_get_id(dc_fw_info, ARRAY_SIZE(dc_fw_info), res_pec);
> +	id = dc_subdev_get_id(dc_fw_info, res_pec);
>  	if (id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", id);
>  		return id;
> diff --git a/drivers/gpu/drm/imx/dc/dc-lb.c b/drivers/gpu/drm/imx/dc/dc-lb.c
> index 38f966625d382..34ea61c2de87d 100644
> --- a/drivers/gpu/drm/imx/dc/dc-lb.c
> +++ b/drivers/gpu/drm/imx/dc/dc-lb.c
> @@ -76,6 +76,7 @@ static const struct dc_subdev_info dc_lb_info[] = {
>  	{ .reg_start = 0x56180bc0, .id = 1, },
>  	{ .reg_start = 0x56180be0, .id = 2, },
>  	{ .reg_start = 0x56180c00, .id = 3, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_lb_pec_regmap_access_ranges[] = {
> @@ -273,7 +274,7 @@ static int dc_lb_bind(struct device *dev, struct device *master, void *data)
>  	if (IS_ERR(lb->reg_cfg))
>  		return PTR_ERR(lb->reg_cfg);
>
> -	lb->id = dc_subdev_get_id(dc_lb_info, ARRAY_SIZE(dc_lb_info), res_pec);
> +	lb->id = dc_subdev_get_id(dc_lb_info, res_pec);
>  	if (lb->id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", lb->id);
>  		return lb->id;
> diff --git a/drivers/gpu/drm/imx/dc/dc-tc.c b/drivers/gpu/drm/imx/dc/dc-tc.c
> index 0bfd381b2cea1..f44b68c0a5e6d 100644
> --- a/drivers/gpu/drm/imx/dc/dc-tc.c
> +++ b/drivers/gpu/drm/imx/dc/dc-tc.c
> @@ -28,6 +28,7 @@
>  static const struct dc_subdev_info dc_tc_info[] = {
>  	{ .reg_start = 0x5618c800, .id = 0, },
>  	{ .reg_start = 0x5618e400, .id = 1, },
> +	{ /* sentinel */ },
>  };
>
>  static const struct regmap_range dc_tc_regmap_ranges[] = {
> @@ -91,7 +92,7 @@ static int dc_tc_bind(struct device *dev, struct device *master, void *data)
>  	if (IS_ERR(tc->reg))
>  		return PTR_ERR(tc->reg);
>
> -	id = dc_subdev_get_id(dc_tc_info, ARRAY_SIZE(dc_tc_info), res);
> +	id = dc_subdev_get_id(dc_tc_info, res);
>  	if (id < 0) {
>  		dev_err(dev, "failed to get instance number: %d\n", id);
>  		return id;
> --
> 2.51.0
>