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    SubjectRe: mmotm 2009-07-16-14-32 - sudden OOPS at boot in ACPI code
    On Mon, 20 Jul 2009, Valdis.Kletnieks@vt.edu wrote:
    > On Thu, 16 Jul 2009 14:34:02 PDT, akpm@linux-foundation.org said:
    > > The mm-of-the-moment snapshot 2009-07-16-14-32 has been uploaded to
    >
    > Dies a horrid death during early boot. Dell Latitude D820, and this graphics:
    >
    > 01:00.0 VGA compatible controller: nVidia Corporation G72M [Quadro NVS 110M/GeForce Go 7300] (rev a1)

    Oh yes, I was getting just the same with Intel graphics (i915);
    but promptly forgot about it once I'd a workaround in place,
    and moved on to other things, sorry.

    >
    > Traceback (hand-copied from a very crappy cell-phone picture)
    >
    > strcmp+0x4/0x1f
    > acpi_device+probe+0xac/0x13e
    > driver_probe_device+0xc9/0x14e
    > __driver_attach+0x58/0x7c
    > ? __driver_attach+0x58/0x7c
    > ? __driver_attach+0x58/0x7c
    > bus_for_each_dev+0x54/0x89
    > driver_attach+0x19/0x1b
    > bus_add_driver+0xv4/0x1fe
    > driver_register+0xb7/0x128
    > ? acpi_video_init+0x0/0x17
    > acpi_bus_register_driver+0x3e/0x42
    > acpi_video_register+0x42/0x6e
    > acpi_video_init+0x15/0x17
    > do_one_initcall+0x56/0x130
    >
    > Analysis shows it's the following code from (inlined) acpi_device_install_notify_handler
    >
    > static int acpi_device_install_notify_handler(struct acpi_device *device)
    > {
    > acpi_status status;
    > char *hid;
    >
    > hid = acpi_device_hid(device);
    > if (!strcmp(hid, ACPI_BUTTON_HID_POWERF))
    >
    > but we never check if hid is non-trash before feeding it to strcmp. Looks
    > like something in this linux-next commit is involved:
    >
    > commit ed444824932d2a563858d82ec1ea29b0aa775e91
    > Author: Bob Moore <robert.moore@intel.com>
    > Date: Mon Jun 29 13:39:29 2009 +0800
    >
    > I suspect something in acpi_get_object_info() is going astray, causing
    > acpi_device_set_id() to set the ->pnp.hardware_id to NULL in this code:
    >
    > if (hid) {
    > device->pnp.hardware_id = ACPI_ALLOCATE_ZEROED(strlen (hid) + 1);
    > if (device->pnp.hardware_id) {
    > strcpy(device->pnp.hardware_id, hid);
    > device->flags.hardware_id = 1;
    > }
    > } else
    > device->pnp.hardware_id = NULL;
    >
    > The else clause is new in this commit.

    I think pnp.hardware_id has changed from being a builtin array to
    an allocated pointer: so before there was always a zeroed array to
    strcmp against, whereas now there's a NULL pointer if you come to
    use acpi_device_install_notify_handler() "too early".

    Patch that works for me at the bottom.

    >
    > Looking at the old code, it *may* be that the ACPI code on my laptop is just
    > busticated and/or there's no _HID method for the graphics card, and the old
    > code Just Happened To Work in previous kernels because ->pnp.hardware_id
    > wouldn't actually get set *at all* in acpi_device_set_id, so we'd get random
    > stale data that was bogus, but didn't give strcmp() indigestion...
    >
    > Any wisdom on debugging this further (including how to tell if the ACPI
    > tables have a sane _HID method for the graphics card) would be appreciated...
    >
    > Or is the correct fix in fact to just add a 'if (!hid) return -EINVAL;' to
    > acpi_device_install_notify_handler()?

    [PATCH mmotm] acpi: work around NULL hardware_id

    Work around NULL pnp.hardware_id in acpi_device_install_notify_handler()
    when probing video device.

    Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
    ---
    Signoff provided to handle the unlikely event that this hack
    is actually the right fix!

    drivers/acpi/scan.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- mmotm/drivers/acpi/scan.c 2009-07-17 12:53:20.000000000 +0100
    +++ linux/drivers/acpi/scan.c 2009-07-17 21:19:10.000000000 +0100
    @@ -376,12 +376,12 @@ static int acpi_device_install_notify_ha
    char *hid;

    hid = acpi_device_hid(device);
    - if (!strcmp(hid, ACPI_BUTTON_HID_POWERF))
    + if (hid && !strcmp(hid, ACPI_BUTTON_HID_POWERF))
    status =
    acpi_install_fixed_event_handler(ACPI_EVENT_POWER_BUTTON,
    acpi_device_notify_fixed,
    device);
    - else if (!strcmp(hid, ACPI_BUTTON_HID_SLEEPF))
    + else if (hid && !strcmp(hid, ACPI_BUTTON_HID_SLEEPF))
    status =
    acpi_install_fixed_event_handler(ACPI_EVENT_SLEEP_BUTTON,
    acpi_device_notify_fixed,

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