linux-kernel - Re: [RFC] firmware loader: retry _nowait requests when userhelper is not yet available

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Date:	Tue, 06 Mar 2012 01:42:54 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Christian Lamparter <chunkeey@...glemail.com>
CC:	linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
	alan@...rguk.ukuu.org.uk, "Rafael J. Wysocki" <rjw@...k.pl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: [RFC] firmware loader: retry _nowait requests when userhelper
 is not yet available


[ Adding more Cc's. ]

On 03/04/2012 01:52 AM, Christian Lamparter wrote:

> During resume, the userhelper might not be available. However for
> drivers which use the request_firmware_nowait interface, this will
> only lead to a pointless WARNING and a device which no longer works
> after the resume [since it couldn't get the firmware, because the
> userhelper was not available to take the request].
> 
> In order to solve this "chicken or egg" dilemma, the code now
> retries _nowait requests at one second intervals until the
> "loading_timeout" time is up.
> 
> ---
> I'm aware about the previous "request_firmware* in probe" discussions.
> Unfortunately, the hardware needs firmware so there is no other way
> around it. So please, I just wanted to know what the general opinion
> about the idea behind this patch is.
> 
> Regards,
> 	Christian
> 
> BTW: I'm not on the list, so please keep the 'CC'.
> ---
>  drivers/base/firmware_class.c |   24 +++++++++++++++++++++++-
>  1 files changed, 23 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index 6c9387d..9f70096 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -19,6 +19,7 @@
>  #include <linux/kthread.h>
>  #include <linux/highmem.h>
>  #include <linux/firmware.h>
> +#include <linux/delay.h>
>  #include <linux/slab.h>
> 
>  #define to_dev(obj) container_of(obj, struct device, kobj)
> @@ -535,6 +536,11 @@ static int _request_firmware(const struct firmware **firmware_p,
> 
>  	read_lock_usermodehelper();
> 
> +	if (nowait && usermodehelper_is_disabled()) {
> +		retval = -EBUSY;
> +		goto out;
> +	}
> +
>  	if (WARN_ON(usermodehelper_is_disabled())) {
>  		dev_err(device, "firmware: %s will not be loaded\n", name);
>  		retval = -EBUSY;
> @@ -633,7 +639,7 @@ static int request_firmware_work_func(void *arg)
>  {
>  	struct firmware_work *fw_work = arg;
>  	const struct firmware *fw;
> -	int ret;
> +	int ret, timeout = loading_timeout;
> 
>  	if (!arg) {
>  		WARN_ON(1);
> @@ -642,6 +648,22 @@ static int request_firmware_work_func(void *arg)
> 
>  	ret = _request_firmware(&fw, fw_work->name, fw_work->device,
>  				fw_work->uevent, true);
> +
> +	while (ret == -EBUSY) {
> +		/*
> +		 * Try to retrieve the firmware within the loading timeout.
> +		 * To stick with the loading timeout convention from above:
> +		 *	loading_timeout = 0 means 'try forever' as well.
> +		 */
> +
> +		msleep(1000);
> +		ret = _request_firmware(&fw, fw_work->name, fw_work->device,
> +					fw_work->uevent, true);
> +
> +		if (timeout != 0 && timeout-- == 1)

> +			break;

> +	};

> +

>  	fw_work->cont(fw, fw_work->context);
> 
>  	module_put(fw_work->module);

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