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

Hi

On Thu, Feb 13, 2014 at 4:21 PM, Benjamin Tissoires
[off-list ref] wrote:

On Wed, Feb 12, 2014 at 5:25 AM, David Herrmann [off-list ref] wrote:

quoted

Hi

On Mon, Feb 10, 2014 at 6:58 PM, Benjamin Tissoires
[off-list ref] wrote:

quoted

.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 <redacted>
---
 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 :)

quoted

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

good idea.

quoted

quoted

+}
+
 /*
  * 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?

Yeah, we should allocate the +7 size, but we shouldn't use it as
"length" argument. We should just silently guarantee the buffer is big
enough.

Thanks
David

Cheers,
Benjamin

quoted

quoted

+
+       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 <redacted>

Thanks
David

quoted

 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