Re: [PATCH 03/14] HID: core: implement generic .request()

[Benjamin Tissoires]

On Wed, Feb 12, 2014 at 5:25 AM, David Herrmann <dh.herrmann@xxxxxxxxx> wrote:
> Hi
>
> On Mon, Feb 10, 2014 at 6:58 PM, Benjamin Tissoires
> <benjamin.tissoires@xxxxxxxxxx> wrote:
>> .request() can be emulated through .raw_request()
>> we can implement this emulation in hid-core, and make .request
>> not mandatory for transport layer drivers.
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
>> ---
>>  drivers/hid/hid-core.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
>>  include/linux/hid.h    |  5 ++++-
>>  2 files changed, 48 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
>> index 18fe49b..f36778a 100644
>> --- a/drivers/hid/hid-core.c
>> +++ b/drivers/hid/hid-core.c
>> @@ -1248,6 +1248,11 @@ void hid_output_report(struct hid_report *report, __u8 *data)
>>  }
>>  EXPORT_SYMBOL_GPL(hid_output_report);
>>
>> +static int hid_report_len(struct hid_report *report)
>> +{
>> +       return ((report->size - 1) >> 3) + 1 + (report->id > 0) + 7;
>
> Just for clarity, this is equivalent to the following, right?
>
> return DIV_ROUND_UP(report->size, 8) + !!(report->id > 0) + 7;

yes, it should (at least that's what I understand too :)

>
> I always have to read that shifting code twice to get it.. Maybe add a
> comment explaining the different entries here.

good idea.

>
>> +}
>> +
>>  /*
>>   * Allocator for buffer that is going to be passed to hid_output_report()
>>   */
>> @@ -1258,7 +1263,7 @@ u8 *hid_alloc_report_buf(struct hid_report *report, gfp_t flags)
>>          * of implement() working on 8 byte chunks
>>          */
>>
>> -       int len = ((report->size - 1) >> 3) + 1 + (report->id > 0) + 7;
>> +       int len = hid_report_len(report);
>>
>>         return kmalloc(len, flags);
>>  }
>> @@ -1314,6 +1319,44 @@ static struct hid_report *hid_get_report(struct hid_report_enum *report_enum,
>>         return report;
>>  }
>>
>> +/*
>> + * Implement a generic .request() callback, using .raw_request()
>> + * DO NOT USE in hid drivers directly, but through hid_hw_request instead.
>> + */
>> +void __hid_request(struct hid_device *hid, struct hid_report *report,
>> +               int reqtype)
>> +{
>> +       char *buf;
>> +       int ret;
>> +       int len;
>> +
>> +       if (!hid->ll_driver->raw_request)
>> +               return;
>> +
>> +       buf = hid_alloc_report_buf(report, GFP_KERNEL);
>> +       if (!buf)
>> +               return;
>> +
>> +       len = hid_report_len(report);

actually, after sending the patches, I was wondering if we should use
the +7 in hid_report_len.
"len" is used in .raw_request(), and the +7 was only for the implement(), right?

So maybe a device can reject this because the size of the report is too big...

Jiri, David, any ideas?

Cheers,
Benjamin

>> +
>> +       if (reqtype == HID_REQ_SET_REPORT)
>> +               hid_output_report(report, buf);
>> +
>> +       ret = hid->ll_driver->raw_request(hid, report->id, buf, len,
>> +                                         report->type, reqtype);
>> +       if (ret < 0) {
>> +               dbg_hid("unable to complete request: %d\n", ret);
>> +               goto out;
>> +       }
>> +
>> +       if (reqtype == HID_REQ_GET_REPORT)
>> +               hid_input_report(hid, report->type, buf, ret, 0);
>> +
>> +out:
>> +       kfree(buf);
>> +}
>> +EXPORT_SYMBOL_GPL(__hid_request);
>> +
>
> Looks good to me.
>
> Reviewed-by: David Herrmann <dh.herrmann@xxxxxxxxx>
>
> Thanks
> David
>
>>  int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, int size,
>>                 int interrupt)
>>  {
>> diff --git a/include/linux/hid.h b/include/linux/hid.h
>> index a837ede..09fbbd7 100644
>> --- a/include/linux/hid.h
>> +++ b/include/linux/hid.h
>> @@ -753,6 +753,7 @@ struct hid_field *hidinput_get_led_field(struct hid_device *hid);
>>  unsigned int hidinput_count_leds(struct hid_device *hid);
>>  __s32 hidinput_calc_abs_res(const struct hid_field *field, __u16 code);
>>  void hid_output_report(struct hid_report *report, __u8 *data);
>> +void __hid_request(struct hid_device *hid, struct hid_report *rep, int reqtype);
>>  u8 *hid_alloc_report_buf(struct hid_report *report, gfp_t flags);
>>  struct hid_device *hid_allocate_device(void);
>>  struct hid_report *hid_register_report(struct hid_device *device, unsigned type, unsigned id);
>> @@ -965,7 +966,9 @@ static inline void hid_hw_request(struct hid_device *hdev,
>>                                   struct hid_report *report, int reqtype)
>>  {
>>         if (hdev->ll_driver->request)
>> -               hdev->ll_driver->request(hdev, report, reqtype);
>> +               return hdev->ll_driver->request(hdev, report, reqtype);
>> +
>> +       __hid_request(hdev, report, reqtype);
>>  }
>>
>>  /**
>> --
>> 1.8.3.1
>>
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