[alsa-devel] Sample program for hwdep interface

Stefan Richter stefanr at s5r6.in-berlin.de
Sun Jan 12 14:22:30 CET 2014

On Jan 05 Takashi Sakamoto wrote:
> This program just demonstrates how to use hwdep interface.
> For Fireworks, via this interface, FFADO can use all of implemented 
> commands without failures. And it's my solution for this ticket.
> Here, I try to describe the detail related to this ticket[1].
> I should have mentioned the detail in ffado-devel but I got the whole 
> picture in the end of last year.
> Cause:
> The bug is due to failure of some commands in some models.
> The commands are 'EfcGetClockCmd' and 'EfcPolledValuesCmd'.
> These commands are used to get device status.
> The bug appears in initializing process of FFADO.
> So this bug affects both streaming and mixer/control functionality.
> In the end of last year, I had a contact in Echo Audio.
> I asked the implementation of 'Echo Fireworks Command/Response' over 
> 'AV/C vendor dependent' command.
> The person answered that some commands are not implemented on current 
> firmware for reported models.
> (I have no information for the reason.)
> The person also said that there are no differences between firmwares 
> installed by drivers of Windows/OS X.
> A solution:
> Using these addresses for command/response.
> An issue:
> Using an address range for response has an issue.
> The address range is an exclusive-resource in an system [2].
> In my opinion, considering ALSA/FFADO, it's better that such resource is used
> in kernel-land driver and the driver gives an interface to use it for user-land
> application.
> Of cource, there is another way, to use this resource just in
> one user-land application such as ffado-dbus-server.
> Then I need to make another way for kernel-land driver.
> (Maybe implementing alternative AV/C commands)
> [1] http://subversion.ffado.org/ticket/360
> [2] http://mailman.alsa-project.org/pipermail/alsa-devel/2013-December/070447.html

Takashi and Clemens,

another alternative would be to implement sharing/multiplexing of the EFC
response address range in firewire-core, like it is implemented for
FCP_COMMAND and FCP_RESPONSE.  Not sure if it is wise to share nonstandard
address ranges though.
Stefan Richter
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