[PATCH 105/379][SRU][OEM-5.6] bus: mhi: core: Fix channel device name conflict

[You-Sheng Yang]

From: Jeffrey Hugo <jhugo at codeaurora.org>

BugLink: https://bugs.launchpad.net/bugs/1879633

When multiple instances of the same MHI product are present in a system,
we can see a splat from mhi_create_devices() - "sysfs: cannot create
duplicate filename".

This is because the device names assigned to the MHI channel devices are
non-unique.  They consist of the channel's name, and the channel's pipe
id.  For identical products, each instance is going to have the same
set of channel (both in name and pipe id).

To fix this, we prepend the device name of the parent device that the
MHI channels belong to.  Since different instances of the same product
should have unique device names, this makes the MHI channel devices for
each product also unique.

Additionally, remove the pipe id from the MHI channel device name.  This
is an internal detail to the MHI product that provides little value, and
imposes too much device specific internal details to userspace.  It is
expected that channel with a specific name (ie "SAHARA") has a specific
client, and it does not matter what pipe id that channel is enumerated on.
The pipe id is an internal detail between the MHI bus, and the hardware.
The client is not expected to make decisions based on the pipe id, and to
do so would require the client to have intimate knowledge of the hardware,
which is inappropiate as it may violate the layering provided by the MHI
bus.  The limitation of doing this is that each product may only have one
instance of a channel by a unique name.  This limitation is appropriate
given the usecases of MHI channels.

Signed-off-by: Jeffrey Hugo <jhugo at codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk at codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam at linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam at linaro.org>
Link: https://lore.kernel.org/r/20200430190555.32741-7-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit f0e1d3ac2d7c16a5d2c9d67f5a61133db7681af8)
Signed-off-by: You-Sheng Yang <vicamo.yang at canonical.com>
---
 drivers/bus/mhi/core/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 936524065128..c26eed06e5cc 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -328,7 +328,8 @@ void mhi_create_devices(struct mhi_controller *mhi_cntrl)
 
 		/* Channel name is same for both UL and DL */
 		mhi_dev->chan_name = mhi_chan->name;
-		dev_set_name(&mhi_dev->dev, "%04x_%s", mhi_chan->chan,
+		dev_set_name(&mhi_dev->dev, "%s_%s",
+			     dev_name(mhi_cntrl->cntrl_dev),
 			     mhi_dev->chan_name);
 
 		/* Init wakeup source if available */
-- 
2.29.2