> On 05/12/2014 09:03 AM, Benjamin Tissoires wrote:
>> Hi Srinivas,
>>
>> On Sat, May 10, 2014 at 2:48 PM, Srinivas Pandruvada
>> <srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote:
>>> Hi Benjamin,
>>>
>>> On 05/08/2014 07:28 AM, Benjamin Tissoires wrote:
>>>> On Thu, May 8, 2014 at 9:32 AM, Archana Patni
>>>> <archana.patni@xxxxxxxxxxxxxxx> wrote:
>>>>> Some i2c_hid devices like a sensor hub have built-in fifos which
>>>>> can accumulate input events in their buffers and trigger an interrupt
>>>>> at end of a user defined event like fifo full or a timeout. The
>>>>> current
>>>>> implementation reads one event at a time in the IRQ handler leading
>>>>> to
>>>>> several hundred interrupts being necessary to flush the fifo.
>>>>>
>>>>> This patch changes the threaded IRQ handler to keep input events
>>>>> until
>>>>> there are no input events left to read. In the normal case, this will
>>>>> invoke one additional call to fetch an input event to check for no
>>>>> pending
>>>>> events and terminate the loop.
>>>> I must say, I don't like this patch.
>>>> It seems to me that it will solve your problem but will break other
>>>> devices. Nothing in the spec says what happens if the host tries to
>>>> read while the interrupt line is *not* asserted. I can easily imagine
>>>> several scenarios where the device would hang until the next available
>>>> data, or will just fail.
>>>>
>>>> So the proper way according to the spec is to check the status of the
>>>> interrupt line. This line is the responsibility of the device to be
>>>> asserted and we should rely on it to know if we can read again.
>>>>
>>>> However, a quick check on the interrupt API did not provide me the
>>>> function I would like, so I guess this is something to be work on.
>>>>
>>>> I can not ack this one until we can be sure not breaking other stuff.
>>>>
>>>> So: NACK.
>>> I understand your reason, there may be some HID device which will have
>>> issue
>>> with this change.
>>> I am interested in throwing some idea, as I am trying to keep the
>>> devices in
>>> deepest idle states as
>>> long as possible. Sensors are one of the offenders.
>>> - This driver can register i2c_driver, command callback. We can define
>>> one
>>> of the command to set the set the max size dynamically or fire this
>>> logic to
>>> empty buffers. This way, we can only enable such logic, when a sensor
>>> hub
>>> has capability and notifies this capability dynamically without
>>> affecting
>>> any other hid devices.
>> I am OK with the logic as long as the i2c calls are independent of the
>> HID layer. Remember that if the advertised bus is BUS_I2C, it might as
>> well be an uhid device which will not handle the i2c calls.
>>
>> Another solution could be to add a HID quirk which triggers the "empty
>> while input are here" and set this quirk in hid-sensor-hub. This way,
>> you will be in control of it and other devices might use it as well if
>> they support it.
>>
>> I am not a big fan of quirks, so I would still prefer your solution if
>> you can control it without disturbing the HID subsystem. This will all
>> depend where you can enable the functionality on the device.
> I also don't like quirks as they start becoming de facto solutions.
>
> Archana,
>
> Can you prototype this using i2c_client_commands by keeping above
> constraints?
>
> Thanks,
> Srinivas
Benjamin,
The i2c_clients_command callback hook seems to be deprecated and not
widely used. We had a quick check with Srinivas and he asked us to fall
back to a quirk based approach.
We will create a device specific quirk (using vendor ID) which sets up a
batched read IRQ handler if it sees a device capable of supporting batch
reads from the fifo. In the normal case, the current IRQ handler will
continue to be used. As more devices support this feature, they can turn
on the batched handler via the quirk.
Does this look ok to you ?
Thanks
Archana
>
>
>> Cheers,
>> Benjamin
>>
>>> Thanks,
>>> Srinivas
>>>
>>>
>>>> Cheers,
>>>> Benjamin
>>>>
>>>>> Signed-off-by: Archana Patni <archana.patni@xxxxxxxxx>
>>>>> Signed-off-by: Subramony Sesha <subramony.sesha@xxxxxxxxx>
>>>>> Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxx>
>>>>> Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxx>
>>>>> ---
>>>>> drivers/hid/i2c-hid/i2c-hid.c | 20 +++++++++++++-------
>>>>> 1 file changed, 13 insertions(+), 7 deletions(-)
>>>>>
>>>>> diff --git a/drivers/hid/i2c-hid/i2c-hid.c
>>>>> b/drivers/hid/i2c-hid/i2c-hid.c
>>>>> index 21aafc8..3f09a50 100644
>>>>> --- a/drivers/hid/i2c-hid/i2c-hid.c
>>>>> +++ b/drivers/hid/i2c-hid/i2c-hid.c
>>>>> @@ -52,6 +52,7 @@
>>>>> static bool debug;
>>>>> module_param(debug, bool, 0444);
>>>>> MODULE_PARM_DESC(debug, "print a lot of debug information");
>>>>> +#define MAX_INPUT_EVENT_READ 100
>>>>>
>>>>> #define i2c_hid_dbg(ihid, fmt, arg...)
>>>>> \
>>>>> do {
>>>>> \
>>>>> @@ -366,7 +367,7 @@ static int i2c_hid_hwreset(struct i2c_client
>>>>> *client)
>>>>> return 0;
>>>>> }
>>>>>
>>>>> -static void i2c_hid_get_input(struct i2c_hid *ihid)
>>>>> +static int i2c_hid_get_input(struct i2c_hid *ihid)
>>>>> {
>>>>> int ret, ret_size;
>>>>> int size = le16_to_cpu(ihid->hdesc.wMaxInputLength);
>>>>> @@ -374,11 +375,11 @@ static void i2c_hid_get_input(struct i2c_hid
>>>>> *ihid)
>>>>> ret = i2c_master_recv(ihid->client, ihid->inbuf, size);
>>>>> if (ret != size) {
>>>>> if (ret < 0)
>>>>> - return;
>>>>> + return ret;
>>>>>
>>>>> dev_err(&ihid->client->dev, "%s: got %d data
>>>>> instead of
>>>>> %d\n",
>>>>> __func__, ret, size);
>>>>> - return;
>>>>> + return -EIO;
>>>>> }
>>>>>
>>>>> ret_size = ihid->inbuf[0] | ihid->inbuf[1] << 8;
>>>>> @@ -387,13 +388,13 @@ static void i2c_hid_get_input(struct i2c_hid
>>>>> *ihid)
>>>>> /* host or device initiated RESET completed */
>>>>> if (test_and_clear_bit(I2C_HID_RESET_PENDING,
>>>>> &ihid->flags))
>>>>> wake_up(&ihid->wait);
>>>>> - return;
>>>>> + return 0;
>>>>> }
>>>>>
>>>>> if (ret_size > size) {
>>>>> dev_err(&ihid->client->dev, "%s: incomplete report
>>>>> (%d/%d)\n",
>>>>> __func__, size, ret_size);
>>>>> - return;
>>>>> + return -EIO;
>>>>> }
>>>>>
>>>>> i2c_hid_dbg(ihid, "input: %*ph\n", ret_size, ihid->inbuf);
>>>>> @@ -402,17 +403,22 @@ static void i2c_hid_get_input(struct i2c_hid
>>>>> *ihid)
>>>>> hid_input_report(ihid->hid, HID_INPUT_REPORT,
>>>>> ihid->inbuf + 2,
>>>>> ret_size - 2, 1);
>>>>>
>>>>> - return;
>>>>> + return 1;
>>>>> }
>>>>>
>>>>> static irqreturn_t i2c_hid_irq(int irq, void *dev_id)
>>>>> {
>>>>> struct i2c_hid *ihid = dev_id;
>>>>> + int ret;
>>>>> + int count = 0;
>>>>>
>>>>> if (test_bit(I2C_HID_READ_PENDING, &ihid->flags))
>>>>> return IRQ_HANDLED;
>>>>> + do {
>>>>> + count++;
>>>>> + ret = i2c_hid_get_input(ihid);
>>>>>
>>>>> - i2c_hid_get_input(ihid);
>>>>> + } while (count < MAX_INPUT_EVENT_READ && ret > 0);
>>>>>
>>>>> return IRQ_HANDLED;
>>>>> }
>>>>> --
>>>>> 1.7.9.5
>>>>>
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