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    SubjectRe: [PATCH 2/3] mwifiex: support sysfs initiated device coredump
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    On 2/21/2018 11:59 PM, Brian Norris wrote:
    > On Wed, Feb 21, 2018 at 11:50:19AM +0100, Arend van Spriel wrote:
    >> Since commit 3c47d19ff4dc ("drivers: base: add coredump driver ops")
    >> it is possible to initiate a device coredump from user-space. This
    >> patch adds support for it adding the .coredump() driver callback.
    >> As there is no longer a need to initiate it through debugfs remove
    >> that code.
    >>
    >> Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
    >> ---
    >> drivers/net/wireless/marvell/mwifiex/debugfs.c | 31 +-------------------------
    >> drivers/net/wireless/marvell/mwifiex/pcie.c | 19 ++++++++++++++--
    >> drivers/net/wireless/marvell/mwifiex/sdio.c | 13 +++++++++++
    >> drivers/net/wireless/marvell/mwifiex/usb.c | 14 ++++++++++++
    >> 4 files changed, 45 insertions(+), 32 deletions(-)
    >
    > The documentation doesn't really say [1], but is the coredump supposed
    > to happen synchronously? Because the mwifiex implementation is
    > asynchronous, whereas it looks like the brcmfmac one is synchronous.

    Well, that depends on the eye of the beholder I guess. From user-space
    perspective it is asynchronous regardless. A write access to the
    coredump sysfs file eventually results in a uevent when the devcoredump
    entry is created, ie. after driver has made a dev_coredump API call.
    Whether the driver does that synchronously or asynchronously is
    irrelevant as far as user-space is concerned.

    > Brian
    >
    > [1] In fact, the ABI documentation really just describes kernel
    > internals, rather than documenting any user-facing details, from what I
    > can tell.

    You are right. Clearly I did not reach the end my learning curve here. I
    assumed referring to the existing dev_coredump facility was sufficient,
    but maybe it is worth a patch to be more explicit and mention the uevent
    behavior. Also dev_coredump facility may be disabled upon which the
    trigger will have no effect in sysfs. In the kernel the data passed by
    the driver is simply freed by dev_coredump facility.

    Regards,
    Arend

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