Re: [PATCH v5 05/16] drm/vkms: Add dummy pixel_read/pixel_write callbacks to avoid NULL pointers
Le 25/03/24 - 10:59, Maíra Canal a écrit :
> On 3/13/24 14:44, Louis Chauvet wrote:
> > Introduce two callbacks which does nothing. They are used in replacement
> > of NULL and it avoid kernel OOPS if this NULL is called.
> >
> > If those callback are used, it means that there is a mismatch between
> > what formats are announced by atomic_check and what is realy supported by
> > atomic_update.
> >
> > Signed-off-by: Louis Chauvet
> > ---
> > drivers/gpu/drm/vkms/vkms_formats.c | 43
> > +++--
> > 1 file changed, 37 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_formats.c
> > b/drivers/gpu/drm/vkms/vkms_formats.c
> > index 55a4365d21a4..b57d85b8b935 100644
> > --- a/drivers/gpu/drm/vkms/vkms_formats.c
> > +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> > @@ -136,6 +136,21 @@ static void RGB565_to_argb_u16(u8 *in_pixel, struct
> > pixel_argb_u16 *out_pixel)
> > out_pixel->b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
> > }
> >
> > +/**
> > + * black_to_argb_u16() - pixel_read callback which always read black
> > + *
> > + * This callback is used when an invalid format is requested for plane
> > reading.
> > + * It is used to avoid null pointer to be used as a function. In theory,
> > this function should
> > + * never be called, except if you found a bug in the driver/DRM core.
> > + */
> > +static void black_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16
> > *out_pixel)
> > +{
> > + out_pixel->a = (u16)0x;
> > + out_pixel->r = 0;
> > + out_pixel->g = 0;
> > + out_pixel->b = 0;
> > +}
> > +
> > /**
> >* vkms_compose_row - compose a single row of a plane
> >* @stage_buffer: output line with the composed pixels
> > @@ -238,6 +253,16 @@ static void argb_u16_to_RGB565(u8 *out_pixel, struct
> > pixel_argb_u16 *in_pixel)
> > *pixel = cpu_to_le16(r << 11 | g << 5 | b);
> > }
> >
> > +/**
> > + * argb_u16_to_nothing() - pixel_write callback with no effect
> > + *
> > + * This callback is used when an invalid format is requested for writeback.
> > + * It is used to avoid null pointer to be used as a function. In theory,
> > this should never
> > + * happen, except if there is a bug in the driver
> > + */
> > +static void argb_u16_to_nothing(u8 *out_pixel, struct pixel_argb_u16
> > *in_pixel)
> > +{}
> > +
> > /**
> >* Generic loop for all supported writeback format. It is executed just
> > after the blending to
> >* write a line in the writeback buffer.
> > @@ -261,8 +286,8 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
> >
> > /**
> >* Retrieve the correct read_pixel function for a specific format.
> > - * The returned pointer is NULL for unsupported pixel formats. The caller
> > must ensure that the
> > - * pointer is valid before using it in a vkms_plane_state.
> > + * If the format is not supported by VKMS a warn is emitted and a dummy
> > "always read black"
>
> "If the format is not supported by VKMS, a warning is emitted and a
> dummy "always read black"..."
Fixed in v6.
> > + * function is returned.
> >*
> >* @format: DRM_FORMAT_* value for which to obtain a conversion function
> > (see [drm_fourcc.h])
> >*/
> > @@ -285,18 +310,21 @@ pixel_read_t get_pixel_read_function(u32 format)
> > * format must:
> > * - Be listed in vkms_formats in vkms_plane.c
> > * - Have a pixel_read callback defined here
> > +*
> > +* To avoid kernel crash, a dummy "always read black" function
> > is used. It means
> > +* that during the composition, this plane will always be black.
> > */
> > WARN(true,
> > "Pixel format %p4cc is not supported by VKMS planes. This
> > is a kernel bug, atomic check must forbid this configuration.\n",
> > );
> > - return (pixel_read_t)NULL;
> > + return _to_argb_u16;
> > }
> > }
> >
> > /**
> >* Retrieve the correct write_pixel function for a specific format.
> > - * The returned pointer is NULL for unsupported pixel formats. The caller
> > must ensure that the
> > - * pointer is valid before using it in a vkms_writeback_job.
> > + * If the format is not supported by VKMS a warn is emitted and a dummy
> > "don't do anything"
>
> "If the format is not supported by VKMS, a warning is emitted and a
> dummy "don't do anything"..."
Fixed in v6.
Thanks,
Louis Chauvet
> Best Regards,
> - Maíra
>
> > + * function is returned.
> >*
> >* @format: DRM_FORMAT_* value for which to obtain a conversion function
> > (see [drm_fourcc.h])
> >*/
> > @@ -319,10 +347,13 @@ pixel_write_t get_pixel_write_function(u32 format)
> > * format must:
> > * - Be listed in vkms_wb_formats in vkms_writeback.c
> > * - Have a pixel_write callback defined here
> > +*
> > +* To avoid kernel crash, a dummy "don't
Re: [PATCH v5 05/16] drm/vkms: Add dummy pixel_read/pixel_write callbacks to avoid NULL pointers
Le 25/03/24 - 14:05, Pekka Paalanen a écrit :
> On Wed, 13 Mar 2024 18:44:59 +0100
> Louis Chauvet wrote:
>
> > Introduce two callbacks which does nothing. They are used in replacement
> > of NULL and it avoid kernel OOPS if this NULL is called.
> >
> > If those callback are used, it means that there is a mismatch between
> > what formats are announced by atomic_check and what is realy supported by
> > atomic_update.
> >
> > Signed-off-by: Louis Chauvet
> > ---
> > drivers/gpu/drm/vkms/vkms_formats.c | 43
> > +++--
> > 1 file changed, 37 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_formats.c
> > b/drivers/gpu/drm/vkms/vkms_formats.c
> > index 55a4365d21a4..b57d85b8b935 100644
> > --- a/drivers/gpu/drm/vkms/vkms_formats.c
> > +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> > @@ -136,6 +136,21 @@ static void RGB565_to_argb_u16(u8 *in_pixel, struct
> > pixel_argb_u16 *out_pixel)
> > out_pixel->b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
> > }
> >
> > +/**
> > + * black_to_argb_u16() - pixel_read callback which always read black
> > + *
> > + * This callback is used when an invalid format is requested for plane
> > reading.
> > + * It is used to avoid null pointer to be used as a function. In theory,
> > this function should
> > + * never be called, except if you found a bug in the driver/DRM core.
> > + */
> > +static void black_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16
> > *out_pixel)
> > +{
> > + out_pixel->a = (u16)0x;
> > + out_pixel->r = 0;
> > + out_pixel->g = 0;
> > + out_pixel->b = 0;
> > +}
> > +
> > /**
> > * vkms_compose_row - compose a single row of a plane
> > * @stage_buffer: output line with the composed pixels
> > @@ -238,6 +253,16 @@ static void argb_u16_to_RGB565(u8 *out_pixel, struct
> > pixel_argb_u16 *in_pixel)
> > *pixel = cpu_to_le16(r << 11 | g << 5 | b);
> > }
> >
> > +/**
> > + * argb_u16_to_nothing() - pixel_write callback with no effect
> > + *
> > + * This callback is used when an invalid format is requested for writeback.
> > + * It is used to avoid null pointer to be used as a function. In theory,
> > this should never
> > + * happen, except if there is a bug in the driver
> > + */
> > +static void argb_u16_to_nothing(u8 *out_pixel, struct pixel_argb_u16
> > *in_pixel)
> > +{}
> > +
> > /**
> > * Generic loop for all supported writeback format. It is executed just
> > after the blending to
> > * write a line in the writeback buffer.
> > @@ -261,8 +286,8 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
> >
> > /**
> > * Retrieve the correct read_pixel function for a specific format.
> > - * The returned pointer is NULL for unsupported pixel formats. The caller
> > must ensure that the
> > - * pointer is valid before using it in a vkms_plane_state.
> > + * If the format is not supported by VKMS a warn is emitted and a dummy
> > "always read black"
> > + * function is returned.
> > *
> > * @format: DRM_FORMAT_* value for which to obtain a conversion function
> > (see [drm_fourcc.h])
> > */
> > @@ -285,18 +310,21 @@ pixel_read_t get_pixel_read_function(u32 format)
> > * format must:
> > * - Be listed in vkms_formats in vkms_plane.c
> > * - Have a pixel_read callback defined here
> > +*
> > +* To avoid kernel crash, a dummy "always read black" function
> > is used. It means
> > +* that during the composition, this plane will always be black.
> > */
> > WARN(true,
> > "Pixel format %p4cc is not supported by VKMS planes. This
> > is a kernel bug, atomic check must forbid this configuration.\n",
> > );
> > - return (pixel_read_t)NULL;
> > + return _to_argb_u16;
>
> Hi Louis,
>
> I'm perhaps a bit paranoid in these things, but I'd make this not
> black. Maybe something more "screaming" like magenta. There is a slight
> chance that black might sometimes be expected, or not affect the
> result. After all, blending something into black with pre-multiplied
> alpha is equivalent to no-blending (a copy). The kernel warning is
> good, the magenta is more like an assurance.
Changed to 0xFF/0x00/0XFF in the V6.
Thanks,
Louis Chauvet
> Anyway,
>
> Acked-by: Pekka Paalanen
>
>
> Thanks,
> pq
>
>
> > }
> > }
> >
> > /**
> > * Retrieve the correct write_pixel function for a specific format.
> > - * The returned pointer is NULL for unsupported pixel formats. The caller
> > must ensure that the
> > - * pointer is valid before using it in a vkms_writeback_job.
> > + * If the format is not supported by VKMS a warn is emitted and a dummy
> > "don't do anything"
> > + * function is returned.
> > *
> > * @format: DRM_FORMAT_* value for which to obtain a conversion function
> > (see [drm_fourcc.h])
> > */
> > @@ -319,10 +347,13 @@ pixel_write_t
Re: [PATCH v5 05/16] drm/vkms: Add dummy pixel_read/pixel_write callbacks to avoid NULL pointers
On 3/13/24 14:44, Louis Chauvet wrote:
Introduce two callbacks which does nothing. They are used in replacement
of NULL and it avoid kernel OOPS if this NULL is called.
If those callback are used, it means that there is a mismatch between
what formats are announced by atomic_check and what is realy supported by
atomic_update.
Signed-off-by: Louis Chauvet
---
drivers/gpu/drm/vkms/vkms_formats.c | 43 +++--
1 file changed, 37 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/vkms/vkms_formats.c
b/drivers/gpu/drm/vkms/vkms_formats.c
index 55a4365d21a4..b57d85b8b935 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -136,6 +136,21 @@ static void RGB565_to_argb_u16(u8 *in_pixel, struct
pixel_argb_u16 *out_pixel)
out_pixel->b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
}
+/**
+ * black_to_argb_u16() - pixel_read callback which always read black
+ *
+ * This callback is used when an invalid format is requested for plane reading.
+ * It is used to avoid null pointer to be used as a function. In theory, this
function should
+ * never be called, except if you found a bug in the driver/DRM core.
+ */
+static void black_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
+{
+ out_pixel->a = (u16)0x;
+ out_pixel->r = 0;
+ out_pixel->g = 0;
+ out_pixel->b = 0;
+}
+
/**
* vkms_compose_row - compose a single row of a plane
* @stage_buffer: output line with the composed pixels
@@ -238,6 +253,16 @@ static void argb_u16_to_RGB565(u8 *out_pixel, struct
pixel_argb_u16 *in_pixel)
*pixel = cpu_to_le16(r << 11 | g << 5 | b);
}
+/**
+ * argb_u16_to_nothing() - pixel_write callback with no effect
+ *
+ * This callback is used when an invalid format is requested for writeback.
+ * It is used to avoid null pointer to be used as a function. In theory, this
should never
+ * happen, except if there is a bug in the driver
+ */
+static void argb_u16_to_nothing(u8 *out_pixel, struct pixel_argb_u16 *in_pixel)
+{}
+
/**
* Generic loop for all supported writeback format. It is executed just after
the blending to
* write a line in the writeback buffer.
@@ -261,8 +286,8 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
/**
* Retrieve the correct read_pixel function for a specific format.
- * The returned pointer is NULL for unsupported pixel formats. The caller must
ensure that the
- * pointer is valid before using it in a vkms_plane_state.
+ * If the format is not supported by VKMS a warn is emitted and a dummy "always
read black"
"If the format is not supported by VKMS, a warning is emitted and a
dummy "always read black"..."
+ * function is returned.
*
* @format: DRM_FORMAT_* value for which to obtain a conversion function (see
[drm_fourcc.h])
*/
@@ -285,18 +310,21 @@ pixel_read_t get_pixel_read_function(u32 format)
* format must:
* - Be listed in vkms_formats in vkms_plane.c
* - Have a pixel_read callback defined here
+*
+* To avoid kernel crash, a dummy "always read black" function
is used. It means
+* that during the composition, this plane will always be black.
*/
WARN(true,
"Pixel format %p4cc is not supported by VKMS planes. This is a
kernel bug, atomic check must forbid this configuration.\n",
);
- return (pixel_read_t)NULL;
+ return _to_argb_u16;
}
}
/**
* Retrieve the correct write_pixel function for a specific format.
- * The returned pointer is NULL for unsupported pixel formats. The caller must
ensure that the
- * pointer is valid before using it in a vkms_writeback_job.
+ * If the format is not supported by VKMS a warn is emitted and a dummy "don't do
anything"
"If the format is not supported by VKMS, a warning is emitted and a
dummy "don't do anything"..."
Best Regards,
- Maíra
+ * function is returned.
*
* @format: DRM_FORMAT_* value for which to obtain a conversion function (see
[drm_fourcc.h])
*/
@@ -319,10 +347,13 @@ pixel_write_t get_pixel_write_function(u32 format)
* format must:
* - Be listed in vkms_wb_formats in vkms_writeback.c
* - Have a pixel_write callback defined here
+*
+* To avoid kernel crash, a dummy "don't do anything" function
is used. It means
+* that the resulting writeback buffer is not composed and can
contains any values.
*/
WARN(true,
"Pixel format %p4cc is not supported by VKMS writeback. This is
a kernel bug, atomic check must forbid this configuration.\n",
);
- return (pixel_write_t)NULL;
+ return _u16_to_nothing;
}
}
Re: [PATCH v5 05/16] drm/vkms: Add dummy pixel_read/pixel_write callbacks to avoid NULL pointers
On Wed, 13 Mar 2024 18:44:59 +0100
Louis Chauvet wrote:
> Introduce two callbacks which does nothing. They are used in replacement
> of NULL and it avoid kernel OOPS if this NULL is called.
>
> If those callback are used, it means that there is a mismatch between
> what formats are announced by atomic_check and what is realy supported by
> atomic_update.
>
> Signed-off-by: Louis Chauvet
> ---
> drivers/gpu/drm/vkms/vkms_formats.c | 43
> +++--
> 1 file changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_formats.c
> b/drivers/gpu/drm/vkms/vkms_formats.c
> index 55a4365d21a4..b57d85b8b935 100644
> --- a/drivers/gpu/drm/vkms/vkms_formats.c
> +++ b/drivers/gpu/drm/vkms/vkms_formats.c
> @@ -136,6 +136,21 @@ static void RGB565_to_argb_u16(u8 *in_pixel, struct
> pixel_argb_u16 *out_pixel)
> out_pixel->b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
> }
>
> +/**
> + * black_to_argb_u16() - pixel_read callback which always read black
> + *
> + * This callback is used when an invalid format is requested for plane
> reading.
> + * It is used to avoid null pointer to be used as a function. In theory,
> this function should
> + * never be called, except if you found a bug in the driver/DRM core.
> + */
> +static void black_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
> +{
> + out_pixel->a = (u16)0x;
> + out_pixel->r = 0;
> + out_pixel->g = 0;
> + out_pixel->b = 0;
> +}
> +
> /**
> * vkms_compose_row - compose a single row of a plane
> * @stage_buffer: output line with the composed pixels
> @@ -238,6 +253,16 @@ static void argb_u16_to_RGB565(u8 *out_pixel, struct
> pixel_argb_u16 *in_pixel)
> *pixel = cpu_to_le16(r << 11 | g << 5 | b);
> }
>
> +/**
> + * argb_u16_to_nothing() - pixel_write callback with no effect
> + *
> + * This callback is used when an invalid format is requested for writeback.
> + * It is used to avoid null pointer to be used as a function. In theory,
> this should never
> + * happen, except if there is a bug in the driver
> + */
> +static void argb_u16_to_nothing(u8 *out_pixel, struct pixel_argb_u16
> *in_pixel)
> +{}
> +
> /**
> * Generic loop for all supported writeback format. It is executed just
> after the blending to
> * write a line in the writeback buffer.
> @@ -261,8 +286,8 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
>
> /**
> * Retrieve the correct read_pixel function for a specific format.
> - * The returned pointer is NULL for unsupported pixel formats. The caller
> must ensure that the
> - * pointer is valid before using it in a vkms_plane_state.
> + * If the format is not supported by VKMS a warn is emitted and a dummy
> "always read black"
> + * function is returned.
> *
> * @format: DRM_FORMAT_* value for which to obtain a conversion function
> (see [drm_fourcc.h])
> */
> @@ -285,18 +310,21 @@ pixel_read_t get_pixel_read_function(u32 format)
>* format must:
>* - Be listed in vkms_formats in vkms_plane.c
>* - Have a pixel_read callback defined here
> + *
> + * To avoid kernel crash, a dummy "always read black" function
> is used. It means
> + * that during the composition, this plane will always be black.
>*/
> WARN(true,
>"Pixel format %p4cc is not supported by VKMS planes. This
> is a kernel bug, atomic check must forbid this configuration.\n",
>);
> - return (pixel_read_t)NULL;
> + return _to_argb_u16;
Hi Louis,
I'm perhaps a bit paranoid in these things, but I'd make this not
black. Maybe something more "screaming" like magenta. There is a slight
chance that black might sometimes be expected, or not affect the
result. After all, blending something into black with pre-multiplied
alpha is equivalent to no-blending (a copy). The kernel warning is
good, the magenta is more like an assurance.
Anyway,
Acked-by: Pekka Paalanen
Thanks,
pq
> }
> }
>
> /**
> * Retrieve the correct write_pixel function for a specific format.
> - * The returned pointer is NULL for unsupported pixel formats. The caller
> must ensure that the
> - * pointer is valid before using it in a vkms_writeback_job.
> + * If the format is not supported by VKMS a warn is emitted and a dummy
> "don't do anything"
> + * function is returned.
> *
> * @format: DRM_FORMAT_* value for which to obtain a conversion function
> (see [drm_fourcc.h])
> */
> @@ -319,10 +347,13 @@ pixel_write_t get_pixel_write_function(u32 format)
>* format must:
>* - Be listed in vkms_wb_formats in vkms_writeback.c
>* - Have a pixel_write callback defined here
> + *
> + * To avoid kernel crash, a dummy "don't do anything" function
> is used. It means
> + * that the resulting
Re: [PATCH v5 05/16] drm/vkms: Add dummy pixel_read/pixel_write callbacks to avoid NULL pointers
On 3/13/24 10:44, Louis Chauvet wrote: > Introduce two callbacks which does nothing. They are used in replacement > of NULL and it avoid kernel OOPS if this NULL is called. > > If those callback are used, it means that there is a mismatch between > what formats are announced by atomic_check and what is realy supported by > atomic_update. > > Signed-off-by: Louis Chauvet > --- > drivers/gpu/drm/vkms/vkms_formats.c | 43 > +++-- > 1 file changed, 37 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/vkms/vkms_formats.c > b/drivers/gpu/drm/vkms/vkms_formats.c > index 55a4365d21a4..b57d85b8b935 100644 > --- a/drivers/gpu/drm/vkms/vkms_formats.c > +++ b/drivers/gpu/drm/vkms/vkms_formats.c > @@ -261,8 +286,8 @@ void vkms_writeback_row(struct vkms_writeback_job *wb, > > /** Please mak this comment conform to kernel-doc format or don't use "/**" to begin the comment. > * Retrieve the correct read_pixel function for a specific format. > - * The returned pointer is NULL for unsupported pixel formats. The caller > must ensure that the > - * pointer is valid before using it in a vkms_plane_state. > + * If the format is not supported by VKMS a warn is emitted and a dummy > "always read black" > + * function is returned. > * > * @format: DRM_FORMAT_* value for which to obtain a conversion function > (see [drm_fourcc.h]) > */ > @@ -285,18 +310,21 @@ pixel_read_t get_pixel_read_function(u32 format) >* format must: >* - Be listed in vkms_formats in vkms_plane.c >* - Have a pixel_read callback defined here > + * > + * To avoid kernel crash, a dummy "always read black" function > is used. It means > + * that during the composition, this plane will always be black. >*/ > WARN(true, >"Pixel format %p4cc is not supported by VKMS planes. This > is a kernel bug, atomic check must forbid this configuration.\n", >); > - return (pixel_read_t)NULL; > + return _to_argb_u16; > } > } > > /** Same here. > * Retrieve the correct write_pixel function for a specific format. > - * The returned pointer is NULL for unsupported pixel formats. The caller > must ensure that the > - * pointer is valid before using it in a vkms_writeback_job. > + * If the format is not supported by VKMS a warn is emitted and a dummy > "don't do anything" > + * function is returned. > * > * @format: DRM_FORMAT_* value for which to obtain a conversion function > (see [drm_fourcc.h]) > */ thanks. -- #Randy
[PATCH v5 05/16] drm/vkms: Add dummy pixel_read/pixel_write callbacks to avoid NULL pointers
Introduce two callbacks which does nothing. They are used in replacement
of NULL and it avoid kernel OOPS if this NULL is called.
If those callback are used, it means that there is a mismatch between
what formats are announced by atomic_check and what is realy supported by
atomic_update.
Signed-off-by: Louis Chauvet
---
drivers/gpu/drm/vkms/vkms_formats.c | 43 +++--
1 file changed, 37 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/vkms/vkms_formats.c
b/drivers/gpu/drm/vkms/vkms_formats.c
index 55a4365d21a4..b57d85b8b935 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -136,6 +136,21 @@ static void RGB565_to_argb_u16(u8 *in_pixel, struct
pixel_argb_u16 *out_pixel)
out_pixel->b = drm_fixp2int_round(drm_fixp_mul(fp_b, fp_rb_ratio));
}
+/**
+ * black_to_argb_u16() - pixel_read callback which always read black
+ *
+ * This callback is used when an invalid format is requested for plane reading.
+ * It is used to avoid null pointer to be used as a function. In theory, this
function should
+ * never be called, except if you found a bug in the driver/DRM core.
+ */
+static void black_to_argb_u16(u8 *in_pixel, struct pixel_argb_u16 *out_pixel)
+{
+ out_pixel->a = (u16)0x;
+ out_pixel->r = 0;
+ out_pixel->g = 0;
+ out_pixel->b = 0;
+}
+
/**
* vkms_compose_row - compose a single row of a plane
* @stage_buffer: output line with the composed pixels
@@ -238,6 +253,16 @@ static void argb_u16_to_RGB565(u8 *out_pixel, struct
pixel_argb_u16 *in_pixel)
*pixel = cpu_to_le16(r << 11 | g << 5 | b);
}
+/**
+ * argb_u16_to_nothing() - pixel_write callback with no effect
+ *
+ * This callback is used when an invalid format is requested for writeback.
+ * It is used to avoid null pointer to be used as a function. In theory, this
should never
+ * happen, except if there is a bug in the driver
+ */
+static void argb_u16_to_nothing(u8 *out_pixel, struct pixel_argb_u16 *in_pixel)
+{}
+
/**
* Generic loop for all supported writeback format. It is executed just after
the blending to
* write a line in the writeback buffer.
@@ -261,8 +286,8 @@ void vkms_writeback_row(struct vkms_writeback_job *wb,
/**
* Retrieve the correct read_pixel function for a specific format.
- * The returned pointer is NULL for unsupported pixel formats. The caller must
ensure that the
- * pointer is valid before using it in a vkms_plane_state.
+ * If the format is not supported by VKMS a warn is emitted and a dummy
"always read black"
+ * function is returned.
*
* @format: DRM_FORMAT_* value for which to obtain a conversion function (see
[drm_fourcc.h])
*/
@@ -285,18 +310,21 @@ pixel_read_t get_pixel_read_function(u32 format)
* format must:
* - Be listed in vkms_formats in vkms_plane.c
* - Have a pixel_read callback defined here
+*
+* To avoid kernel crash, a dummy "always read black" function
is used. It means
+* that during the composition, this plane will always be black.
*/
WARN(true,
"Pixel format %p4cc is not supported by VKMS planes. This
is a kernel bug, atomic check must forbid this configuration.\n",
);
- return (pixel_read_t)NULL;
+ return _to_argb_u16;
}
}
/**
* Retrieve the correct write_pixel function for a specific format.
- * The returned pointer is NULL for unsupported pixel formats. The caller must
ensure that the
- * pointer is valid before using it in a vkms_writeback_job.
+ * If the format is not supported by VKMS a warn is emitted and a dummy "don't
do anything"
+ * function is returned.
*
* @format: DRM_FORMAT_* value for which to obtain a conversion function (see
[drm_fourcc.h])
*/
@@ -319,10 +347,13 @@ pixel_write_t get_pixel_write_function(u32 format)
* format must:
* - Be listed in vkms_wb_formats in vkms_writeback.c
* - Have a pixel_write callback defined here
+*
+* To avoid kernel crash, a dummy "don't do anything" function
is used. It means
+* that the resulting writeback buffer is not composed and can
contains any values.
*/
WARN(true,
"Pixel format %p4cc is not supported by VKMS writeback.
This is a kernel bug, atomic check must forbid this configuration.\n",
);
- return (pixel_write_t)NULL;
+ return _u16_to_nothing;
}
}
--
2.43.0
