Re: [PATCH] MMC: fix sdhci-dove removal

Russell King - ARM Linux
2012-10-15T10:37:30Z

On Mon, Oct 15, 2012 at 10:43:48AM +0100, Russell King - ARM Linux wrote:
> 1. Unregister the device _BEFORE_ taking away any resources it may
> be using.
> 2. Don't check clks against NULL.
>
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Looking at this driver some more, who the hell came up with the sdhci
registration interface? It violates one of the most fundamental
principles of kernel driver programming. You do _NOT_ publish your
driver interfaces _UNTIL_ you have finished setting your device up.
Otherwise, in a preemptible or SMP kernel, your driver can be used
before the initialization has completed.

As this driver calls sdhci_pltfm_register() before it has obtained the
clock for the interface, and this function does:
sdhci_pltfm_init
sdhci_add_host
mmc_add_host
mmc_start_host
mmc_power_up
mmc_set_ios
sdhci_set_ios

See, we're trying to power up and clock the card _before_ the dove
sdhci driver has even claimed the clock let alone enabled it. This
is total bollocks. The sdhci platform interface is total crap for
creating this broken design in the first place. This is why MMC has
the init + add interfaces, they're there to allow drivers to do stuff
the Right(tm) way and avoid shit like the above.

This should have been picked up at review time before the driver went
into mainline. In any case, it needs to be fixed.