Re: [PATCH 2/5] spi: i.MX: Move to coredevice_initcall

[Sascha Hauer <s.hauer@pengutronix.de>]

On Sun, May 11, 2014 at 10:49:26PM +0400, Alexander Shiyan wrote:
> Thu,  8 May 2014 09:31:36 +0200 от Sascha Hauer <s.hauer@pengutronix.de>:
> > SPI is often used by other devices, so make sure it's initialized
> > early.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  drivers/spi/imx_spi.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/spi/imx_spi.c b/drivers/spi/imx_spi.c
> > index e07cf1a..3146339 100644
> > --- a/drivers/spi/imx_spi.c
> > +++ b/drivers/spi/imx_spi.c
> > @@ -586,4 +586,4 @@ static struct driver_d imx_spi_driver = {
> >  	.of_compatible = DRV_OF_COMPAT(imx_spi_dt_ids),
> >  	.id_table = imx_spi_ids,
> >  };
> > -device_platform_driver(imx_spi_driver);
> > +coredevice_platform_driver(imx_spi_driver);
> > -- 
> 
> Maybe we should put all drivers in a single runlevel and implement
> handle of EPROBE_DEFER?

I think about EPROBE_DEFER for longer now. What has hold me back was
that we would have to release all resources before returning
EPROBE_DEFER. Most drivers don't have proper error pathes implemented
and I don't see much gain in fixing this. For a bootloader the error
release pathes are unnecessary overhead, because nobody will ever
use the same resources again (at least without EPROBE_DEFER).
My recent idea to work around that issue is this:

- put the drivers private data into dev->priv
- when returning an error from probe, instead of freeing the data
  keep it.
- when probing again re-use the data.

With this drivers could be written like:

	priv = dev->priv;
	if (!priv) {
		priv = xzalloc(sizeof(priv));
		dev->priv = priv;
	}

	if (!priv->clk) {
		clk = clk_get(dev, NULL);
		if (IS_ERR(clk))
			return PTR_ERR(clk);
		priv->clk = clk;
		clk_enable(priv->clk);
	}

	if (!priv->regulator) {
		regulator = regulator_get(dev, "vmmc");
		if (IS_ERR(regulator))
			return PTR_ERR(regulator);
		priv->regulator = regulator;
	}

This way drivers could allocate the missing resources as needed without
freeing them between different calls to probe().

Sascha

-- 
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