[PATCH] drm: Grab reference of connector before return connector from sun4i_tcon_get_connector

[PATCH] drm: Grab reference of connector before return connector from sun4i_tcon_get_connector

[He Ying]

From the comments of drm_for_each_connector_iter(), we know
that "connector is only valid within the list body, if you
want to use connector after calling drm_connector_list_iter_end()
then you need to grab your own reference first using
drm_connector_get()". So fix the wrong use of connector
according to the comments and then call drm_connector_put()
after using connector finishes.

Signed-off-by: He Ying <heying24@huawei.com>
---
 drivers/gpu/drm/sun4i/sun4i_tcon.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 9f06dec0fc61..24fa6784ee5f 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -47,12 +47,12 @@ static struct drm_connector *sun4i_tcon_get_connector(const struct drm_encoder *
 	drm_connector_list_iter_begin(encoder->dev, &iter);
 	drm_for_each_connector_iter(connector, &iter)
 		if (connector->encoder == encoder) {
-			drm_connector_list_iter_end(&iter);
-			return connector;
+			drm_connector_get(connector);
+			break;
 		}
 	drm_connector_list_iter_end(&iter);
 
-	return NULL;
+	return connector;
 }
 
 static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
@@ -65,6 +65,7 @@ static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
 		return -EINVAL;
 
 	info = &connector->display_info;
+	drm_connector_put(connector);
 	if (info->num_bus_formats != 1)
 		return -EINVAL;
 
@@ -361,6 +362,7 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
 	/* TODO support normal CPU interface modes */
 	struct sun6i_dsi *dsi = encoder_to_sun6i_dsi(encoder);
 	struct mipi_dsi_device *device = dsi->device;
+	struct drm_connector *connector;
 	u8 bpp = mipi_dsi_pixel_format_to_bpp(device->format);
 	u8 lanes = device->lanes;
 	u32 block_space, start_delay;
@@ -372,7 +374,9 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
 	sun4i_tcon0_mode_set_common(tcon, mode);
 
 	/* Set dithering if needed */
-	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
+	connector = sun4i_tcon_get_connector(encoder);
+	sun4i_tcon0_mode_set_dithering(tcon, connector);
+	drm_connector_put(connector);
 
 	regmap_update_bits(tcon->regs, SUN4I_TCON0_CTL_REG,
 			   SUN4I_TCON0_CTL_IF_MASK,
@@ -430,6 +434,7 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
 				      const struct drm_display_mode *mode)
 {
 	unsigned int bp;
+	struct drm_connector *connector;
 	u8 clk_delay;
 	u32 reg, val = 0;
 
@@ -440,7 +445,9 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
 	sun4i_tcon0_mode_set_common(tcon, mode);
 
 	/* Set dithering if needed */
-	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
+	connector = sun4i_tcon_get_connector(encoder);
+	sun4i_tcon0_mode_set_dithering(tcon, connector);
+	drm_connector_put(connector);
 
 	/* Adjust clock delay */
 	clk_delay = sun4i_tcon_get_clk_delay(mode, 0);
@@ -518,6 +525,7 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 
 	/* Set dithering if needed */
 	sun4i_tcon0_mode_set_dithering(tcon, connector);
+	drm_connector_put(connector);
 
 	/* Adjust clock delay */
 	clk_delay = sun4i_tcon_get_clk_delay(mode, 0);
-- 
2.17.1

Re: [PATCH] drm: Grab reference of connector before return connector from sun4i_tcon_get_connector

[Jani Nikula]

On Mon, 01 Nov 2021, He Ying <heying24@huawei.com> wrote:
> From the comments of drm_for_each_connector_iter(), we know
> that "connector is only valid within the list body, if you
> want to use connector after calling drm_connector_list_iter_end()
> then you need to grab your own reference first using
> drm_connector_get()". So fix the wrong use of connector
> according to the comments and then call drm_connector_put()
> after using connector finishes.
>
> Signed-off-by: He Ying <heying24@huawei.com>

Please use "drm/sun4i:" subject prefix for sun4i patches.

BR,
Jani.


> ---
>  drivers/gpu/drm/sun4i/sun4i_tcon.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index 9f06dec0fc61..24fa6784ee5f 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -47,12 +47,12 @@ static struct drm_connector *sun4i_tcon_get_connector(const struct drm_encoder *
>  	drm_connector_list_iter_begin(encoder->dev, &iter);
>  	drm_for_each_connector_iter(connector, &iter)
>  		if (connector->encoder == encoder) {
> -			drm_connector_list_iter_end(&iter);
> -			return connector;
> +			drm_connector_get(connector);
> +			break;
>  		}
>  	drm_connector_list_iter_end(&iter);
>  
> -	return NULL;
> +	return connector;
>  }
>  
>  static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
> @@ -65,6 +65,7 @@ static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
>  		return -EINVAL;
>  
>  	info = &connector->display_info;
> +	drm_connector_put(connector);
>  	if (info->num_bus_formats != 1)
>  		return -EINVAL;
>  
> @@ -361,6 +362,7 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
>  	/* TODO support normal CPU interface modes */
>  	struct sun6i_dsi *dsi = encoder_to_sun6i_dsi(encoder);
>  	struct mipi_dsi_device *device = dsi->device;
> +	struct drm_connector *connector;
>  	u8 bpp = mipi_dsi_pixel_format_to_bpp(device->format);
>  	u8 lanes = device->lanes;
>  	u32 block_space, start_delay;
> @@ -372,7 +374,9 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
>  	sun4i_tcon0_mode_set_common(tcon, mode);
>  
>  	/* Set dithering if needed */
> -	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
> +	connector = sun4i_tcon_get_connector(encoder);
> +	sun4i_tcon0_mode_set_dithering(tcon, connector);
> +	drm_connector_put(connector);
>  
>  	regmap_update_bits(tcon->regs, SUN4I_TCON0_CTL_REG,
>  			   SUN4I_TCON0_CTL_IF_MASK,
> @@ -430,6 +434,7 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
>  				      const struct drm_display_mode *mode)
>  {
>  	unsigned int bp;
> +	struct drm_connector *connector;
>  	u8 clk_delay;
>  	u32 reg, val = 0;
>  
> @@ -440,7 +445,9 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
>  	sun4i_tcon0_mode_set_common(tcon, mode);
>  
>  	/* Set dithering if needed */
> -	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
> +	connector = sun4i_tcon_get_connector(encoder);
> +	sun4i_tcon0_mode_set_dithering(tcon, connector);
> +	drm_connector_put(connector);
>  
>  	/* Adjust clock delay */
>  	clk_delay = sun4i_tcon_get_clk_delay(mode, 0);
> @@ -518,6 +525,7 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
>  
>  	/* Set dithering if needed */
>  	sun4i_tcon0_mode_set_dithering(tcon, connector);
> +	drm_connector_put(connector);
>  
>  	/* Adjust clock delay */
>  	clk_delay = sun4i_tcon_get_clk_delay(mode, 0);

-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH] drm: Grab reference of connector before return connector from sun4i_tcon_get_connector

[He Ying]

在 2021/11/1 21:02, Jani Nikula 写道:
> On Mon, 01 Nov 2021, He Ying <heying24@huawei.com> wrote:
>>  From the comments of drm_for_each_connector_iter(), we know
>> that "connector is only valid within the list body, if you
>> want to use connector after calling drm_connector_list_iter_end()
>> then you need to grab your own reference first using
>> drm_connector_get()". So fix the wrong use of connector
>> according to the comments and then call drm_connector_put()
>> after using connector finishes.
>>
>> Signed-off-by: He Ying <heying24@huawei.com>
> Please use "drm/sun4i:" subject prefix for sun4i patches.

OK. I'll send a V2 later. By the way, may I have your suggestions about

this patch's content.

Re: [PATCH] drm: Grab reference of connector before return connector from sun4i_tcon_get_connector

[Jani Nikula]

On Tue, 02 Nov 2021, He Ying <heying24@huawei.com> wrote:
> 在 2021/11/1 21:02, Jani Nikula 写道:
>> On Mon, 01 Nov 2021, He Ying <heying24@huawei.com> wrote:
>>>  From the comments of drm_for_each_connector_iter(), we know
>>> that "connector is only valid within the list body, if you
>>> want to use connector after calling drm_connector_list_iter_end()
>>> then you need to grab your own reference first using
>>> drm_connector_get()". So fix the wrong use of connector
>>> according to the comments and then call drm_connector_put()
>>> after using connector finishes.
>>>
>>> Signed-off-by: He Ying <heying24@huawei.com>
>> Please use "drm/sun4i:" subject prefix for sun4i patches.
>
> OK. I'll send a V2 later. By the way, may I have your suggestions about
> this patch's content.

Sorry, I only looked here because of the subject prefix, and would have
skipped it completely with a drm/sun4i prefix. ;)

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center

[PATCH -V2] drm/sun4i: Grab reference of connector before return connector from sun4i_tcon_get_connector

[He Ying]

From the comments of drm_for_each_connector_iter(), we know
that "connector is only valid within the list body, if you
want to use connector after calling drm_connector_list_iter_end()
then you need to grab your own reference first using
drm_connector_get()". So fix the wrong use of connector
according to the comments and then call drm_connector_put()
after using connector finishes.

Signed-off-by: He Ying <heying24@huawei.com>
---

V2:
 Use proper subject prefix

 drivers/gpu/drm/sun4i/sun4i_tcon.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 9f06dec0fc61..24fa6784ee5f 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -47,12 +47,12 @@ static struct drm_connector *sun4i_tcon_get_connector(const struct drm_encoder *
 	drm_connector_list_iter_begin(encoder->dev, &iter);
 	drm_for_each_connector_iter(connector, &iter)
 		if (connector->encoder == encoder) {
-			drm_connector_list_iter_end(&iter);
-			return connector;
+			drm_connector_get(connector);
+			break;
 		}
 	drm_connector_list_iter_end(&iter);
 
-	return NULL;
+	return connector;
 }
 
 static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
@@ -65,6 +65,7 @@ static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
 		return -EINVAL;
 
 	info = &connector->display_info;
+	drm_connector_put(connector);
 	if (info->num_bus_formats != 1)
 		return -EINVAL;
 
@@ -361,6 +362,7 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
 	/* TODO support normal CPU interface modes */
 	struct sun6i_dsi *dsi = encoder_to_sun6i_dsi(encoder);
 	struct mipi_dsi_device *device = dsi->device;
+	struct drm_connector *connector;
 	u8 bpp = mipi_dsi_pixel_format_to_bpp(device->format);
 	u8 lanes = device->lanes;
 	u32 block_space, start_delay;
@@ -372,7 +374,9 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
 	sun4i_tcon0_mode_set_common(tcon, mode);
 
 	/* Set dithering if needed */
-	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
+	connector = sun4i_tcon_get_connector(encoder);
+	sun4i_tcon0_mode_set_dithering(tcon, connector);
+	drm_connector_put(connector);
 
 	regmap_update_bits(tcon->regs, SUN4I_TCON0_CTL_REG,
 			   SUN4I_TCON0_CTL_IF_MASK,
@@ -430,6 +434,7 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
 				      const struct drm_display_mode *mode)
 {
 	unsigned int bp;
+	struct drm_connector *connector;
 	u8 clk_delay;
 	u32 reg, val = 0;
 
@@ -440,7 +445,9 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
 	sun4i_tcon0_mode_set_common(tcon, mode);
 
 	/* Set dithering if needed */
-	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
+	connector = sun4i_tcon_get_connector(encoder);
+	sun4i_tcon0_mode_set_dithering(tcon, connector);
+	drm_connector_put(connector);
 
 	/* Adjust clock delay */
 	clk_delay = sun4i_tcon_get_clk_delay(mode, 0);
@@ -518,6 +525,7 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 
 	/* Set dithering if needed */
 	sun4i_tcon0_mode_set_dithering(tcon, connector);
+	drm_connector_put(connector);
 
 	/* Adjust clock delay */
 	clk_delay = sun4i_tcon_get_clk_delay(mode, 0);
-- 
2.17.1

Re: [PATCH -V2] drm/sun4i: Grab reference of connector before return connector from sun4i_tcon_get_connector

[Maxime Ripard]

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Hi,

On Tue, Nov 02, 2021 at 04:46:28AM -0400, He Ying wrote:
> From the comments of drm_for_each_connector_iter(), we know
> that "connector is only valid within the list body, if you
> want to use connector after calling drm_connector_list_iter_end()
> then you need to grab your own reference first using
> drm_connector_get()". So fix the wrong use of connector
> according to the comments and then call drm_connector_put()
> after using connector finishes.
> 
> Signed-off-by: He Ying <heying24@huawei.com>
> ---
> 
> V2:
>  Use proper subject prefix
> 
>  drivers/gpu/drm/sun4i/sun4i_tcon.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index 9f06dec0fc61..24fa6784ee5f 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -47,12 +47,12 @@ static struct drm_connector *sun4i_tcon_get_connector(const struct drm_encoder *
>  	drm_connector_list_iter_begin(encoder->dev, &iter);
>  	drm_for_each_connector_iter(connector, &iter)
>  		if (connector->encoder == encoder) {
> -			drm_connector_list_iter_end(&iter);
> -			return connector;
> +			drm_connector_get(connector);
> +			break;
>  		}
>  	drm_connector_list_iter_end(&iter);
>  
> -	return NULL;
> +	return connector;

Connector might be uninitialized if we don't find one here

>  }
>  
>  static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
> @@ -65,6 +65,7 @@ static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
>  		return -EINVAL;
>  
>  	info = &connector->display_info;
> +	drm_connector_put(connector);
>  	if (info->num_bus_formats != 1)

We're still accessing connector->display_info here, but it might have been
freed already.

Maxime

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Re: [PATCH -V2] drm/sun4i: Grab reference of connector before return connector from sun4i_tcon_get_connector

[He Ying]

在 2021/11/2 23:03, Maxime Ripard 写道:
> Hi,
>
> On Tue, Nov 02, 2021 at 04:46:28AM -0400, He Ying wrote:
>>  From the comments of drm_for_each_connector_iter(), we know
>> that "connector is only valid within the list body, if you
>> want to use connector after calling drm_connector_list_iter_end()
>> then you need to grab your own reference first using
>> drm_connector_get()". So fix the wrong use of connector
>> according to the comments and then call drm_connector_put()
>> after using connector finishes.
>>
>> Signed-off-by: He Ying <heying24@huawei.com>
>> ---
>>
>> V2:
>>   Use proper subject prefix
>>
>>   drivers/gpu/drm/sun4i/sun4i_tcon.c | 18 +++++++++++++-----
>>   1 file changed, 13 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
>> index 9f06dec0fc61..24fa6784ee5f 100644
>> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
>> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
>> @@ -47,12 +47,12 @@ static struct drm_connector *sun4i_tcon_get_connector(const struct drm_encoder *
>>   	drm_connector_list_iter_begin(encoder->dev, &iter);
>>   	drm_for_each_connector_iter(connector, &iter)
>>   		if (connector->encoder == encoder) {
>> -			drm_connector_list_iter_end(&iter);
>> -			return connector;
>> +			drm_connector_get(connector);
>> +			break;
>>   		}
>>   	drm_connector_list_iter_end(&iter);
>>   
>> -	return NULL;
>> +	return connector;
> Connector might be uninitialized if we don't find one here

Connector should be NULL if we don't find one. The code is

#define drm_for_each_connector_iter(connector, iter) \
    while ((connector = drm_connector_list_iter_next(iter)))

So, when we don't break from the while body, connector

can only be NULL.

>
>>   }
>>   
>>   static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
>> @@ -65,6 +65,7 @@ static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder)
>>   		return -EINVAL;
>>   
>>   	info = &connector->display_info;
>> +	drm_connector_put(connector);
>>   	if (info->num_bus_formats != 1)
> We're still accessing connector->display_info here, but it might have been
> freed already.
Agree. I'll place it after using 'info' finishes in v3.
>
> Maxime