Messages in this thread | | | Subject | Re: [PATCH] perf/smmuv3: Add platform id table for module auto loading | From | Yicong Yang <> | Date | Wed, 9 Aug 2023 14:31:09 +0800 |
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Hi Barry, Liang,
On 2023/8/9 13:47, Barry Song wrote: > On Wed, Aug 9, 2023 at 1:01 PM Liang Li <liliang6@email.cn> wrote: >> >> On 2023-08-07 20:22, Yicong Yang <yangyicong@huawei.com> wrote: >>> From: Yicong Yang <yangyicong@hisilicon.com> >>> >>> On ACPI based system the device is probed by the name directly. If the >>> driver is configured as module it can only be loaded manually. Add the >>> platform id table as well as the module alias then the driver will be >>> loaded automatically by the udev or others once the device added. >>> >> >> Please consider revise the long log to clearly express the purpose of the >> changes in this patch: >> >> - What's the exact issue the patch is addressing >> - Why the changes in this patch can fix the issue or make something working >> - Consider impact of the changes introduced by this patch >> >> These info may help reviewers and maintainers .. and yourself on code merge. > > years ago, i found a good doc regarding this, > https://wiki.archlinux.org/title/Modalias > > guess it is because /lib/modules/$(uname -r)/modules.alias fails to contain smmu > driver without the MODULE_DEVICE_TABLE, isn't it, yicong?
Yes I think it's the reason. I didn't find summary in kernel docs for the modalias as well as the uevent mechanism. Arch wiki has a well illustration for the modalias and suse[1] describes how this is used by the udev for module auto loading.
For my case I'm using a ACPI based arm64 server and after booting the arm_smmuv3_pmu.ko is not auto loaded by the udevd since we aren't providing this information. In order to support this we need to provide this MODULE_DEVICE_TABLE() when the smmu pmu added as a platform device, then the userspace udev can know which module to load after the device is added.
[1] https://documentation.suse.com/sles/15-SP1/html/SLES-all/cha-udev.html#sec-udev-drivers
Thanks.
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