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SubjectRe: [PATCH] spi: mark device nodes only in case of successful instantiation
Hi Ralf,

(Cc i2c)

On Fri, Oct 14, 2016 at 9:31 PM, Ralf Ramsauer
<ralf@ramses-pyramidenbau.de> wrote:
> Instantiated SPI device nodes are marked with OF_POPULATE. This was
> introduced in bd6c164. On unloading, loaded device nodes will of course
> be unmarked. The problem are nodes the fail during initialisation: If a
> node failed during registration, it won't be unloaded and hence never be
> unmarked again.
>
> So if a SPI driver module is unloaded and reloaded, it will skip nodes
> that failed before.
>
> Skip device nodes that are already populated and mark them only in case
> of success.
>
> Fixes: bd6c164 ("spi: Mark instantiated device nodes with OF_POPULATE")
> Signed-off-by: Ralf Ramsauer <ralf@ramses-pyramidenbau.de>
> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> Hi,
>
> imagine the following situation: you loaded a spi driver as module, but
> it fails to instantiate, because of some reasons (e.g. some resources,
> like gpios, might be in use in userspace).
>
> When reloading the driver, _all_ nodes, including previously failed
> ones, should be probed again. This is not the case at the moment.
> Current behaviour only re-registers nodes that were previously
> successfully loaded.
>
> This small patches fixes this behaviour. I stumbled over this while
> working on a spi driver.

Thanks for your patch!

> drivers/spi/spi.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 200ca22..f96a04e 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -1604,12 +1604,15 @@ static void of_register_spi_devices(struct spi_master *master)
> return;
>
> for_each_available_child_of_node(master->dev.of_node, nc) {
> - if (of_node_test_and_set_flag(nc, OF_POPULATED))
> + if (of_node_check_flag(nc, OF_POPULATED))
> continue;
> spi = of_register_spi_device(master, nc);
> - if (IS_ERR(spi))
> + if (IS_ERR(spi)) {
> dev_warn(&master->dev, "Failed to create SPI device for %s\n",
> nc->full_name);
> + continue;
> + }
> + of_node_set_flag(nc, OF_POPULATED);

I think it's safer to keep the atomic test-and-set, but clear the flag on
failure, cfr. of_platform_device_create_pdata() and of_amba_device_create().

Shouldn't of_spi_notify() be fixed, too?

The same issue exists for i2c in of_i2c_register_devices() and of_i2c_notify(),
which is what I had used as an example.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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