From 259a41d9ae8f3689742267f340ad2b159d00b302 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Mon, 18 Sep 2017 08:21:37 -0400 Subject: 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: Shuah Khan Signed-off-by: Mauro Carvalho Chehab --- Documentation/media/uapi/dvb/fe-get-property.rst | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'Documentation/media') diff --git a/Documentation/media/uapi/dvb/fe-get-property.rst b/Documentation/media/uapi/dvb/fe-get-property.rst index 948d2ba84f2c..b69741d9cedf 100644 --- a/Documentation/media/uapi/dvb/fe-get-property.rst +++ b/Documentation/media/uapi/dvb/fe-get-property.rst @@ -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:`` -- cgit v1.2.3