linux-kernel - Re: [PATCH] parport: daisy: do not try to load lowlevel driver

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Message-ID: <20190325175338.2fa290cc@gandalf.local.home>
Date:   Mon, 25 Mar 2019 17:53:38 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [PATCH] parport: daisy: do not try to load lowlevel driver

On Mon, 25 Mar 2019 21:13:25 +0000
Sudip Mukherjee <sudipm.mukherjee@...il.com> wrote:

> Some distros like Suse has an alias for "parport_lowlevel" and that
> alias points to "parport_pc". Now when the parport bus registers, it
> also initialises the daisy driver as the daisy driver is needed to
> check the port when the port is first found. Due to the new device
> model daisy driver will now try to find the parallel ports while trying
> to register its driver so that it can bind with them. Now, since daisy
> driver is loaded while parport bus is initialising the list of parport
> is still empty and it tries to load the lowlevel driver, which has an
> alias set to parport_pc, now causes a deadlock.
> 
> We do not need to search for ports and bind the initial list of ports
> to daisy driver as daisy driver is always the first driver to use the
> new found parport and we know when the parport bus is registering the
> list of parport will always be empty. So, proceed with the daisy_drv
> registration even if the list of parport is empty.
> 
> Fixes: 1aec4211204d ("parport: daisy: use new parport device model")
> Reported-by: Michal Kubecek <mkubecek@...e.cz>
> Reported-by: Steven Rostedt <rostedt@...dmis.org>
> Tested-by: Michal Kubecek <mkubecek@...e.cz>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>

Tested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve