Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit da5516b5 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

media: dvb_frontend: better document the -EPERM condition 



Two readonly ioctls can't be allowed if the frontend device
is opened in read only mode. Explain why.

Reviewed by: Shuah Khan <shuahkh@osg.samsung.com>

Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent ceb22c8e

drivers/media/dvb-core/dvb_frontend.c

+17 −3
Original line number Diff line number Diff line
@@ -1923,9 +1923,23 @@ static int dvb_frontend_ioctl(struct file *file, unsigned int cmd, void *parg) 
		return -ENODEV;

	}



	if ((file->f_flags & O_ACCMODE) == O_RDONLY &&

	    (_IOC_DIR(cmd) != _IOC_READ || cmd == FE_GET_EVENT ||

	     cmd == FE_DISEQC_RECV_SLAVE_REPLY)) {

	/*

	 * If the frontend is opened in read-only mode, only the ioctls

	 * that don't interfere with the tune logic should be accepted.

	 * That allows an external application to monitor the DVB QoS and

	 * statistics parameters.

	 *

	 * That matches all _IOR() ioctls, except for two special cases:

	 *   - FE_GET_EVENT is part of the tuning logic on a DVB application;

	 *   - FE_DISEQC_RECV_SLAVE_REPLY is part of DiSEqC 2.0

	 *     setup

	 * So, those two ioctls should also return -EPERM, as otherwise

	 * reading from them would interfere with a DVB tune application

	 */

	if ((file->f_flags & O_ACCMODE) == O_RDONLY

	    && (_IOC_DIR(cmd) != _IOC_READ

		|| cmd == FE_GET_EVENT

		|| cmd == FE_DISEQC_RECV_SLAVE_REPLY)) {

		up(&fepriv->sem);

		return -EPERM;

	}