Date: Tue, 21 Jan 2014 09:25:31 +0000
From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Greg KH <gregkh@linuxfoundation.org>,
        Tushar Behera <tushar.behera@linaro.org>, linux-kernel@vger.kernel.org,
        linux-serial@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
        jslaby@suse.cz, ben.dooks@codethink.co.uk, broonie@kernel.org
Subject: Re: [PATCH 1/2] serial: samsung: Move uart_register_driver call to
 device probe
Message-ID: <20140121092531.350ab714@alan.etchedpixels.co.uk>
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> > So, let's go back to your original worry, what are you concerned about?
> > A device being removed while probe() is called?
> 
> My concern is that we're turning something which should be simple into
> something unnecessarily complex.  By that, I mean something along the
> lines of:

Or in fact more complex in other cases because your remove may well be
refcounted so the stuff may not be going away in the foo_remove() path.

> 
> static DEFINE_MUTEX(foo_mutex);
> static unsigned foo_devices;
> 
> static int foo_probe(struct platform_device *pdev)
> {
> 	int ret;
> 
> 	mutex_lock(&foo_mutex);
> 	if (foo_devices++ == 0)
> 		uart_register_driver(&driver);
> 
> 	ret = foo_really_probe_device(pdev);

We have atomic_inc_and_test and atomic_dec_and_test so it's
fractionally less ugly.

> in every single serial driver we have...  Wouldn't it just be better to
> fix the major/minor number problem rather than have to add all that code
> repetitively to all those drivers?

Quite.

Although for some drivers I suspect what is actually missing when built
in is

module_init() {
	if (not_the_right_platform())
		return -ENOGOOD;
}

 
Going dynamic is the right fix though. Changing how the driver
registration work is a different (and quite independent) problem.

Alan
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