>This series of change is inspired by BH workqueue available in recent >kernel. >In Linux FireWire subsystem, tasklet softIRQ context has been utilized to >operate 1394 OHCI Isochronous Transmit (IT) and Isochronous Receive (IR) >contexts. The tasklet context is not preferable, as you know. >I have already received a proposal[1][2] to replace the usage of tasklet >with BH workqueue. However, the proposal includes bare replacement for 1394 >OHCI IT, IR, Asynchronous Transmit (AT), and Asynchronous Receive (AR) >contexts with neither any care of actual usage for each context nor >practical test reports. In theory, this kind of change should be done by >step by step with enough amount of evaluation over software design to avoid >any disorder. >In this series of changes, the usage of tasklet for 1394 OHCI IT/IR >contexts is just replaced, as a first step. In 1394 OHCI IR/IT events, >software is expected to process the content of page dedicated to DMA >transmission for each isochronous context. It means that the content can be >processed concurrently per isochronous context. Additionally, the content >of page is immutable as long as the software schedules the transmission >again for the page. It means that the task to process the content can sleep >or be preempted. Due to the characteristics, BH workqueue is _not_ used. >At present, 1394 OHCI driver is responsible for the maintenance of tasklet >context, while in this series of change the core function is responsible >for the maintenance of workqueue and work items. This change is an attempt >to let each implementation focus on own task. >The change affects the following implementations of unit protocols which >operate isochronous contexts: >- firewire-net for IP over 1394 (RFC 2734/3146) >- firedtv >- drivers in ALSA firewire stack for IEC 61883-1/6 >- user space applications >As long as reading their codes, the first two drivers look to require no >change. While the drivers in ALSA firewire stack require change to switch >the type of context in which callback is executed. The series of change >includes a patch for them to adapt to work process context. >Finally, these changes are tested by devices supported by ALSA firewire >stack with/without no-period-wakeup runtime of PCM substream. I also tested >examples in libhinoko[3] as samples of user space applications. Currently I >face no issue. >On the other hand, I have neither tested for firewire-net nor firedtv, >since I have never used these functions. If someone has any experience to >use them, I would request to test the change. >[1] https://lore.kernel.org/lkml/20240403144558.13398-1-apais@xxxxxxxxxxxxxxxxxxx/ >[2] https://github.com/allenpais/for-6.9-bh-conversions/issues/1 >[3] https://git.kernel.org/pub/scm/libs/ieee1394/libhinoko.git/ >Regards Thank you for doing this work. You will probably need to send out a v2 As most of you patches have single line comment instead of Block style Commnents (/* ..*/). Please have it fixed. - Allen >Takashi Sakamoto (5): > firewire: core: allocate workqueue to handle isochronous contexts in > card > firewire: core: add local API for work items scheduled to workqueue > specific to isochronous contexts > firewire: ohci: process IT/IR events in sleepable work process to > obsolete tasklet softIRQ > firewire: core: non-atomic memory allocation for isochronous event to > user client > ALSA: firewire: use nonatomic PCM operation
