drivers/base/bus.c | 78 ++++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 64 insertions(+), 14 deletions(-)
This patch series is to fix issues related to bus_rescan_devices_helper().
The function is improperly used for 2 incompatible scenarios as
explained below:
Scenario A: scan drivers for a single device user specify
- user may care about precise synchronous scanning result, so the
function can not collapse error codes.
Scenario B: scan drivers for all devices of a bus
- user may need to scan drivers for a bus's devices as many as
possible, so the function needs to ignore inconsequential error
codes for a device in order to continue to scan for next device.
Fixed by implementing bus_rescan_single_device() for scenario A
and correcting the function for scenario B.
Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
---
Changes in v2:
- Temporarily drop the change related to bus_type's match() return value
- For this 1/2 change, transfer internal -EPROBE_DEFER to user known
-EAGAIN, correct title, commit message, inline comments.
- For this 2/2 change, Add an extra -EBUSY to ignore, correct title
commit message, inline comments.
- Link to v1: https://lore.kernel.org/r/20240904-bus_match_unlikely-v1-0-122318285261@quicinc.com
---
Zijun Hu (2):
driver core: bus: Fix drivers_probe_store() giving user wrong scanning result
driver core: bus: Correct API bus_rescan_devices() behavior
drivers/base/bus.c | 78 ++++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 64 insertions(+), 14 deletions(-)
---
base-commit: fea64fa04c31426eae512751e0c5342345c5741c
change-id: 20240830-bus_match_unlikely-abe9334bcfd2
Best regards,
--
Zijun Hu <quic_zijuhu@quicinc.com>
On Tue, Oct 22, 2024 at 07:18:00PM +0800, Zijun Hu wrote: > This patch series is to fix issues related to bus_rescan_devices_helper(). > > The function is improperly used for 2 incompatible scenarios as > explained below: > > Scenario A: scan drivers for a single device user specify > - user may care about precise synchronous scanning result, so the > function can not collapse error codes. I do not understand this, what is wrong that this is fixing? > Scenario B: scan drivers for all devices of a bus > - user may need to scan drivers for a bus's devices as many as > possible, so the function needs to ignore inconsequential error > codes for a device in order to continue to scan for next device. How often is that needed? And why can't that still work with the existing code? thanks, greg k-h
On 2024/11/12 19:48, Greg Kroah-Hartman wrote:
> On Tue, Oct 22, 2024 at 07:18:00PM +0800, Zijun Hu wrote:
>> This patch series is to fix issues related to bus_rescan_devices_helper().
>>
>> The function is improperly used for 2 incompatible scenarios as
>> explained below:
>>
>> Scenario A: scan drivers for a single device user specify
>> - user may care about precise synchronous scanning result, so the
>> function can not collapse error codes.
>
> I do not understand this, what is wrong that this is fixing?
>
for scanning drivers for single device, it gives user wrong scanning
result(success or failure).
patch 1/2 is a concrete example.
>> Scenario B: scan drivers for all devices of a bus
>> - user may need to scan drivers for a bus's devices as many as
>> possible, so the function needs to ignore inconsequential error
>> codes for a device in order to continue to scan for next device.
>
> How often is that needed? And why can't that still work with the
> existing code?
>
1) API bus_rescan_devices() invokes it and can't achieve its design
purpose due to error described above.
2) as shown by recent mainlined commit, usage of API
bus_rescan_devices() have been dropped due to some bugs.
Commit: 3d6ebf16438d ("cxl/port: Fix cxl_bus_rescan() vs
bus_rescan_devices()")
3) there are only 2 usages for the API now.
// does not do what the comments say
https://elixir.bootlin.com/linux/v6.11/source/drivers/pcmcia/ds.c#L725
// do multi repeated iterating, can be simplified if fix the API bugs
https://elixir.bootlin.com/linux/v6.11/source/drivers/hid/hid-core.c#L2967
4) i have more reply in below link about the API's bugs.
https://lore.kernel.org/all/20240913-bus_match_unlikely-v2-2-5c0c3bfda2f6@quicinc.com/
we may go to patch 2/2 to continue discussion.
> thanks,
>
> greg k-h
On 2024/11/12 19:48, Greg Kroah-Hartman wrote:
> On Tue, Oct 22, 2024 at 07:18:00PM +0800, Zijun Hu wrote:
>> This patch series is to fix issues related to bus_rescan_devices_helper().
>>
>> The function is improperly used for 2 incompatible scenarios as
>> explained below:
>>
>> Scenario A: scan drivers for a single device user specify
>> - user may care about precise synchronous scanning result, so the
>> function can not collapse error codes.
>
> I do not understand this, what is wrong that this is fixing?
>
for scanning drivers for single device, it gives user wrong scanning
result(success or failure).
patch 1/2 is a concrete example.
>> Scenario B: scan drivers for all devices of a bus
>> - user may need to scan drivers for a bus's devices as many as
>> possible, so the function needs to ignore inconsequential error
>> codes for a device in order to continue to scan for next device.
>
> How often is that needed? And why can't that still work with the
> existing code?
>
1) API bus_rescan_devices() invokes it and can't achieve its design
purpose due to error described above.
2) as shown by recent mainlined commit, usage of API
bus_rescan_devices() have been dropped due to some bugs.
Commit: 3d6ebf16438d ("cxl/port: Fix cxl_bus_rescan() vs
bus_rescan_devices()")
3) there are only 2 usages for the API now.
// does not do what the comments say
https://elixir.bootlin.com/linux/v6.11/source/drivers/pcmcia/ds.c#L725
// do multi repeated iterating, can be simplified if fix the API bugs
https://elixir.bootlin.com/linux/v6.11/source/drivers/hid/hid-core.c#L2967
4) i have more reply in below link about the API's bugs.
https://lore.kernel.org/all/20240913-bus_match_unlikely-v2-2-5c0c3bfda2f6@quicinc.com/
> thanks,
>
> greg k-h
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