On 12/1/2020 12:29 PM, Jakub Kicinski wrote:
> On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote:
>> This patch series adds support for UCI driver. UCI driver enables userspace
>> clients to communicate to external MHI devices like modem and WLAN. UCI driver
>> probe creates standard character device file nodes for userspace clients to
>> perform open, read, write, poll and release file operations. These file
>> operations call MHI core layer APIs to perform data transfer using MHI bus
>> to communicate with MHI device. Patch is tested using arm64 based platform.
>
> Wait, I thought this was for modems.
>
> Why do WLAN devices need to communicate with user space?
>
Why does it matter what type of device it is? Are modems somehow unique
in that they are the only type of device that userspace is allowed to
interact with?
However, I'll bite. Once such usecase would be QMI. QMI is a generic
messaging protocol, and is not strictly limited to the unique operations
of a modem.
Another usecase would be Sahara - a custom file transfer protocol used
for uploading firmware images, and downloading crashdumps.
Off the top of my head, this driver is useful for modems, wlan, and AI
accelerators.
--
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote:
> On 12/1/2020 12:29 PM, Jakub Kicinski wrote:
> > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote:
> >> This patch series adds support for UCI driver. UCI driver enables userspace
> >> clients to communicate to external MHI devices like modem and WLAN. UCI driver
> >> probe creates standard character device file nodes for userspace clients to
> >> perform open, read, write, poll and release file operations. These file
> >> operations call MHI core layer APIs to perform data transfer using MHI bus
> >> to communicate with MHI device. Patch is tested using arm64 based platform.
> >
> > Wait, I thought this was for modems.
> >
> > Why do WLAN devices need to communicate with user space?
> >
>
> Why does it matter what type of device it is? Are modems somehow unique
> in that they are the only type of device that userspace is allowed to
> interact with?
Yes modems are traditionally highly weird and require some serial
device dance I don't even know about.
We have proper interfaces in Linux for configuring WiFi which work
across vendors. Having char device access to WiFi would be a step
back.
> However, I'll bite. Once such usecase would be QMI. QMI is a generic
> messaging protocol, and is not strictly limited to the unique operations
> of a modem.
>
> Another usecase would be Sahara - a custom file transfer protocol used
> for uploading firmware images, and downloading crashdumps.
Thanks, I was asking for use cases, not which proprietary vendor
protocol you can implement over it.
None of the use cases you mention here should require a direct FW -
user space backdoor for WLAN.
> Off the top of my head, this driver is useful for modems, wlan, and AI
> accelerators.
And other Qualcomm products are available as well :/
Kernel is supposed to create abstract interfaces for user space to
utilize. I will never understand why kernel is expected to be in
business of shipping this sort of vendor backdoors :/
On Tue, Dec 01, 2020 at 12:03:02PM -0800, Jakub Kicinski wrote:
> On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote:
> > On 12/1/2020 12:29 PM, Jakub Kicinski wrote:
> > > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote:
> > >> This patch series adds support for UCI driver. UCI driver enables userspace
> > >> clients to communicate to external MHI devices like modem and WLAN. UCI driver
> > >> probe creates standard character device file nodes for userspace clients to
> > >> perform open, read, write, poll and release file operations. These file
> > >> operations call MHI core layer APIs to perform data transfer using MHI bus
> > >> to communicate with MHI device. Patch is tested using arm64 based platform.
> > >
> > > Wait, I thought this was for modems.
> > >
> > > Why do WLAN devices need to communicate with user space?
> > >
> >
> > Why does it matter what type of device it is? Are modems somehow unique
> > in that they are the only type of device that userspace is allowed to
> > interact with?
>
> Yes modems are traditionally highly weird and require some serial
> device dance I don't even know about.
>
> We have proper interfaces in Linux for configuring WiFi which work
> across vendors. Having char device access to WiFi would be a step
> back.
>
This is not for configuring the WiFi. This driver is mostly used for modems and
the AI accelerator Jeff is working on. But there might be a usecase for WLAN
devices as well to collect crash dumps and download fw (typical vendor ways) but
having those features are add-ons IMO.
So I think we should not be blocked by those usecases.
Thanks,
Mani