[PATCHv2] cec-api: log the reason for the -EINVAL in cec_s_mode

[Hans Verkuil]

If cec_debug >= 1 then log why the requested mode returned -EINVAL.

It can be hard to debug this since -EINVAL can be returned for many
reasons. So this should help.

Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
---
Changes since v1:

Removed some error injection code that inadvertently ended up in the patch
I posted.
---
 drivers/media/cec/cec-api.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/media/cec/cec-api.c b/drivers/media/cec/cec-api.c
index 8dd16e263452..00d43d74020f 100644
--- a/drivers/media/cec/cec-api.c
+++ b/drivers/media/cec/cec-api.c
@@ -357,34 +357,47 @@ static long cec_s_mode(struct cec_adapter *adap, struct 
cec_fh *fh,

        if (copy_from_user(&mode, parg, sizeof(mode)))
                return -EFAULT;
-       if (mode & ~(CEC_MODE_INITIATOR_MSK | CEC_MODE_FOLLOWER_MSK))
+       if (mode & ~(CEC_MODE_INITIATOR_MSK | CEC_MODE_FOLLOWER_MSK)) {
+               dprintk(1, "%s: invalid mode bits set\n", __func__);
                return -EINVAL;
+       }

        mode_initiator = mode & CEC_MODE_INITIATOR_MSK;
        mode_follower = mode & CEC_MODE_FOLLOWER_MSK;

        if (mode_initiator > CEC_MODE_EXCL_INITIATOR ||
-           mode_follower > CEC_MODE_MONITOR_ALL)
+           mode_follower > CEC_MODE_MONITOR_ALL) {
+               dprintk(1, "%s: unknown mode\n", __func__);
                return -EINVAL;
+       }

        if (mode_follower == CEC_MODE_MONITOR_ALL &&
-           !(adap->capabilities & CEC_CAP_MONITOR_ALL))
+           !(adap->capabilities & CEC_CAP_MONITOR_ALL)) {
+               dprintk(1, "%s: MONITOR_ALL not supported\n", __func__);
                return -EINVAL;
+       }

        if (mode_follower == CEC_MODE_MONITOR_PIN &&
-           !(adap->capabilities & CEC_CAP_MONITOR_PIN))
+           !(adap->capabilities & CEC_CAP_MONITOR_PIN)) {
+               dprintk(1, "%s: MONITOR_PIN not supported\n", __func__);
                return -EINVAL;
+       }

        /* Follower modes should always be able to send CEC messages */
        if ((mode_initiator == CEC_MODE_NO_INITIATOR ||
             !(adap->capabilities & CEC_CAP_TRANSMIT)) &&
            mode_follower >= CEC_MODE_FOLLOWER &&
-           mode_follower <= CEC_MODE_EXCL_FOLLOWER_PASSTHRU)
+           mode_follower <= CEC_MODE_EXCL_FOLLOWER_PASSTHRU) {
+               dprintk(1, "%s: cannot transmit\n", __func__);
                return -EINVAL;
+       }

        /* Monitor modes require CEC_MODE_NO_INITIATOR */
-       if (mode_initiator && mode_follower >= CEC_MODE_MONITOR_PIN)
+       if (mode_initiator && mode_follower >= CEC_MODE_MONITOR_PIN) {
+               dprintk(1, "%s: monitor modes require NO_INITIATOR\n",
+                       __func__);
                return -EINVAL;
+       }

        /* Monitor modes require CAP_NET_ADMIN */
        if (mode_follower >= CEC_MODE_MONITOR_PIN && !capable(CAP_NET_ADMIN))
-- 
2.13.2