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    Subject[RFC] firmware loader: retry _nowait requests when userhelper is not yet available
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    Date
    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);
    --
    1.7.9.1


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