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

> On Oct 16, 2016, at 12:55 , Ralf Ramsauer <ralf@ramses-pyramidenbau.de> wrote:
>
> Hi Geert,
>
> On 10/16/2016 10:49 AM, Geert Uytterhoeven wrote:
>> 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().
> Ack, no prob. Let me change this in the next version.
>>
>> Shouldn't of_spi_notify() be fixed, too?
> Right, that's almost the same path.
>>
>> The same issue exists for i2c in of_i2c_register_devices() and of_i2c_notify(),
>> which is what I had used as an example.
> Good old c&p ;-)
> I'll fix and test that tomorrow and come back with two patches, as it
> touches different subsystems.
>

Thanks for this. This is a very rare case that’s easy to slip through.
It is good to be consistent :)

> Best
> Ralf
>>

Regards

— Pantelis

>> 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
>>
>
>
> --
> Ralf Ramsauer
> GPG: 0x8F10049B

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