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Commit 259a41d9 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

media: dvb_frontend: fix return values for FE_SET_PROPERTY 



There are several problems with regards to the return of
FE_SET_PROPERTY. The original idea were to return per-property
return codes via tvp->result field, and to return an updated
set of values.

However, that never worked. What's actually implemented is:

- the FE_SET_PROPERTY implementation doesn't call .get_frontend
  callback in order to get the actual parameters after return;

- the tvp->result field is only filled if there's no error.
  So, it is always filled with zero;

- FE_SET_PROPERTY doesn't call memdup_user() nor any other
  copy_to_user() function. So, any changes to the properties
  will be lost;

- FE_SET_PROPERTY is declared as a write-only ioctl (IOW).

While we could fix the above, it could cause regressions.

So, let's just assume what the code really does, updating
the documentation accordingly and removing the logic that
would update the discarded tvp->result.

Reviewed-by: default avatarShuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent da5516b5

Documentation/media/uapi/dvb/fe-get-property.rst

+5 −2
Original line number Diff line number Diff line
@@ -48,8 +48,11 @@ depends on the delivery system and on the device: 


   -  This call requires read/write access to the device.



   -  At return, the values are updated to reflect the actual parameters

      used.

.. note::



   At return, the values aren't updated to reflect the actual

   parameters used. If the actual parameters are needed, an explicit

   call to ``FE_GET_PROPERTY`` is needed.



-  ``FE_GET_PROPERTY:``

drivers/media/dvb-core/dvb_frontend.c

+0 −2
Original line number Diff line number Diff line
@@ -2125,7 +2125,6 @@ static int dvb_frontend_handle_ioctl(struct file *file, 
				kfree(tvp);

				return err;

			}

			(tvp + i)->result = err;

		}

		kfree(tvp);

		break;
@@ -2170,7 +2169,6 @@ static int dvb_frontend_handle_ioctl(struct file *file, 
				kfree(tvp);

				return err;

			}

			(tvp + i)->result = err;

		}



		if (copy_to_user((void __user *)tvps->props, tvp,

include/uapi/linux/dvb/frontend.h

+1 −1
Original line number Diff line number Diff line
@@ -830,7 +830,7 @@ struct dtv_fe_stats { 
 * @cmd:	Digital TV command.

 * @reserved:	Not used.

 * @u:		Union with the values for the command.

 * @result:	Result of the command set (currently unused).

 * @result:	Unused

 *

 * The @u union may have either one of the values below:

 *