On 11/18/2020 12:14 PM, Loic Poulain wrote:
Le mer. 18 nov. 2020 à 19:34, Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx <mailto:jhugo@xxxxxxxxxxxxxx>> a écrit :On 11/18/2020 11:20 AM, Bhaumik Bhatt wrote: > Reset MHI device channels when driver remove is called due to > module unload or any crash scenario. This will make sure that > MHI channels no longer remain enabled for transfers since the > MHI stack does not take care of this anymore after the auto-start > channels feature was removed. > > Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx <mailto:bbhatt@xxxxxxxxxxxxxx>> > --- > net/qrtr/mhi.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c > index 7100f0b..2bf2b19 100644 > --- a/net/qrtr/mhi.c > +++ b/net/qrtr/mhi.c > @@ -104,6 +104,7 @@ static void qcom_mhi_qrtr_remove(struct mhi_device *mhi_dev) > struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev); > > qrtr_endpoint_unregister(&qdev->ep); > + mhi_unprepare_from_transfer(mhi_dev); > dev_set_drvdata(&mhi_dev->dev, NULL); > } > > I admit, I didn't pay much attention to the auto-start being removed, but this seems odd to me. As a client, the MHI device is being removed, likely because of some factor outside of my control, but I still need to clean it up? This really feels like something MHI should be handling.I think this is just about balancing operations, what is done in probe should be undone in remove, so here channels are started in probe and stopped/reset in remove.
I understand that perspective, but that doesn't quite match what is going on here. Regardless of if the channel was started (prepared) in probe, it now needs to be stopped in remove. That not balanced in all cases
Lets assume, in response to probe(), my client driver goes and creates some other object, maybe a socket. In response to that socket being opened/activated by the client of my driver, I go and start the mhi channel. Now, normally, when the socket is closed/deactivated, I stop the MHI channel. In this case, stopping the MHI channel in remove() is unbalanced with respect to probe(), but is now a requirement.
Now you may argue, I should close the object in response to remove, which will then trigger the stop on the channel. That doesn't apply to everything. For example, you cannot close an open file in the kernel. You need to wait for userspace to close it. By the time that happens, the mhi_dev is long gone I expect.
So if, somehow, the client driver is the one causing the remove to occur, then yes it should probably be the one doing the stop, but that's a narrow set of conditions, and I think having that requirement for all scenarios is limiting.
-- Jeffrey Hugo Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
