ftdi_sio usb-serial driver and hotplug

ftdi_sio usb-serial driver and hotplug

[Anton Fedorov]

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Hi guys!

   For my device control i need to have latency set up into 1,
otherwise i have poor performance.

   I can write 1 into /sys/bus/usb_sertial/devices/ttyUSB0/latency_timer,
but only as root, and need to re-write into it after every reconnect device,
that weird.

   I have tried to setup udev, by putting into /etc/udev/rules.d/
   file z99_ftdi.rules with contents:
DRIVER="ftdi_sio", SUBSYSTEM=="usb-serial", ATTR{latency_timer}="1"
   test of rules show that it should correctly write on connection,
   but after reconnect of device it doesn't have latency_timer
   changed -- it still have 16 latency set :(

   Where and what I have missed in rule?

-- 
Best regards,
  Anton
  Call2Ru Service
  datacompboy@call2ru.com

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Re: ftdi_sio usb-serial driver and hotplug

[Kay Sievers]

On Tue, Feb 24, 2009 at 08:38, Anton Fedorov <datacompboy@call2ru.com> wrote:
>   For my device control i need to have latency set up into 1,
> otherwise i have poor performance.
>
>   I can write 1 into /sys/bus/usb_sertial/devices/ttyUSB0/latency_timer,
> but only as root, and need to re-write into it after every reconnect device,
> that weird.
>
>   I have tried to setup udev, by putting into /etc/udev/rules.d/
>   file z99_ftdi.rules with contents:
> DRIVER="ftdi_sio", SUBSYSTEM="usb-serial", ATTR{latency_timer}="1"
>   test of rules show that it should correctly write on connection,
>   but after reconnect of device it doesn't have latency_timer
>   changed -- it still have 16 latency set :(

Try DRIVERS=, it should work here, because the parent device is also
created by the same driver. The driver value may not be set at the
time the event is processed, because the driver is binding to the
device not already bound.

Kay

Re: ftdi_sio usb-serial driver and hotplug

[Anton Fedorov]

В письме от Срд, 25 Фев 2009, 19:25 Kay Sievers пишет:
> On Wed, Feb 25, 2009 at 14:12, Anton Fedorov <datacompboy@call2ru.com> wrote:
>>
>> В письме от Втр, 24 Фев 2009, 22:16 Kay Sievers пишет:
>>>>   I have tried to setup udev, by putting into /etc/udev/rules.d/
>>>>   file z99_ftdi.rules with contents:
>>>> DRIVER="ftdi_sio", SUBSYSTEM="usb-serial", ATTR{latency_timer}="1"
>>>>   test of rules show that it should correctly write on connection,
>>>>   but after reconnect of device it doesn't have latency_timer
>>>>   changed -- it still have 16 latency set :(
>>> Try DRIVERS=, it should work here, because the parent device is also
>>> created by the same driver. The driver value may not be set at the
>>> time the event is processed, because the driver is binding to the
>>> device not already bound.

Sorry for wrong answer last time -- instead of "reply to list" clicked "reply
private" :) yes, you right -- using "DRIVERS=" fixed problem, now latency
correctly set up.
Many thanks!

But why that difference? udevinfo --attribute-walk shows DRIVER="" related to
device, and  http://reactivated.net/writing_udev_rules.html says "you cannot
mix-and-match attributes from multiple parent devices - your rule will not
work".


-- 
Regards,
Anton Fedorov
Call2ru service

Re: ftdi_sio usb-serial driver and hotplug

[Kay Sievers]

On Fri, Feb 27, 2009 at 16:49, Anton Fedorov <datacompboy@call2ru.com> wrote:
>
> В письме от Срд, 25 Фев 2009, 19:25 Kay Sievers пишет:
>> On Wed, Feb 25, 2009 at 14:12, Anton Fedorov <datacompboy@call2ru.com> wrote:
>>>
>>> В письме от Втр, 24 Фев 2009, 22:16 Kay Sievers пишет:
>>>>>   I have tried to setup udev, by putting into /etc/udev/rules.d/
>>>>>   file z99_ftdi.rules with contents:
>>>>> DRIVER="ftdi_sio", SUBSYSTEM="usb-serial", ATTR{latency_timer}="1"
>>>>>   test of rules show that it should correctly write on connection,
>>>>>   but after reconnect of device it doesn't have latency_timer
>>>>>   changed -- it still have 16 latency set :(
>>>> Try DRIVERS=, it should work here, because the parent device is also
>>>> created by the same driver. The driver value may not be set at the
>>>> time the event is processed, because the driver is binding to the
>>>> device not already bound.
>
> Sorry for wrong answer last time -- instead of "reply to list" clicked "reply
> private" :)

Cool.

> yes, you right -- using "DRIVERS=" fixed problem, now latency
> correctly set up.
> Many thanks!

You're welcome.

> But why that difference? udevinfo --attribute-walk shows DRIVER="" related to
> device, and  http://reactivated.net/writing_udev_rules.html says "you cannot
> mix-and-match attributes from multiple parent devices - your rule will not
> work".

Yes, you are "mixing" only  _one_ parent device with the event device. :)

Best,
Kay