Hello!


On 7/31/20 9:43 AM, Yoshihiro Shimoda wrote:

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From: Yuusuke Ashizuka, Sent: Thursday, July 30, 2020 7:02 PM
Subject: [PATCH v2] ravb: Fixed the problem that rmmod can not be done

Thank you for the patch! I found a similar patch for another driver [1].

   It's not the same case -- that driver hadn't had the MDIO release code at all
before that patch.

You're correct. I didn't realized it...

   The patch description was somewhat incomplete there...

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So, we should apply this patch to the ravb driver.

   I believe the driver is innocent. :-)

I hope so :)

   Looks like I was wrong in this case. It's very fortunate that the MDIO bitbang
is not as popular as I thought.

<snip>

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$ lsmod
Module                  Size  Used by
ravb                   40960  1
$ rmmod ravb
rmmod: ERROR: Module ravb is in use

   Shouldn't the driver core call the remove() method for the affected devices
first, before checking the refcount?

In this case, an mii bus of "mdiobb_ops bb_ops" is affected "device" by the ravb driver.
And the ravb driver sets the owner of mii bus as THIS_MODULE like below:

static struct mdiobb_ops bb_ops = {
        .owner = THIS_MODULE,
        .set_mdc = ravb_set_mdc,
        .set_mdio_dir = ravb_set_mdio_dir,
        .set_mdio_data = ravb_set_mdio_data,
        .get_mdio_data = ravb_get_mdio_data,
};

So, I don't think the driver core can call the remove() method for the mii bus
because it's a part of the ravb driver...

   And because the MDIO module just doesn't have the usual method! :-)
(I meant the EtherAVB driver's remove() method, and that one would be called after
a successful reference count check...)

By the way, about the mdio-gpio driver, I'm wondering if the mdio-gpio
driver cannot be removed by rmmod too. (perhaps, we need "rmmod -f" to remove it.)

   You're on your own here. It's fortunate for this patch that I'm not currently loaded
at work! :-)

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By the way, I think you have to send this patch to the following maintainers too:
# We can get it by using scripts/get_maintainers.pl.
David S. Miller [off-list ref] (maintainer:NETWORKING DRIVERS,commit_signer:8/8=100%)
Jakub Kicinski [off-list ref] (maintainer:NETWORKING DRIVERS)

   Not critical, as DaveM uses the patchwork anyway. He started to be CC'ed on netdev patches
only recently. :-)

[...]

Best regards,
Yoshihiro Shimoda

MBR, Sergei