Re: [PATCH v13 0/4] userspace MHI client interface driver

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Jakub Kicinski]

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?

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Jeffrey Hugo]

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.

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Jakub Kicinski]

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 :/

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Jeffrey Hugo]

On 12/1/2020 1:03 PM, 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.

So a WLAN device is only ever allowed to do Wi-Fi?  It can't also have 
GPS functionality for example?

> 
>> 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.

Uploading runtime firmware, with variations based on the runtime mode. 
Flashing the onboard flash based on cryptographic keys.  Accessing 
configuration data.  Accessing device logs.  Configuring device logs. 
Synchronizing the device time reference to Linux local or remote time 
sources.  Enabling debugging/performance hardware.  Getting software 
diagnostic events.  Configuring redundancy hardware per workload. 
Uploading new cryptographic keys.  Invalidating cryptographic keys. 
Uploading factory test data and running factory tests.

Need more?

-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Jakub Kicinski]

On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote:
> On 12/1/2020 1:03 PM, 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.  
> 
> So a WLAN device is only ever allowed to do Wi-Fi?  It can't also have 
> GPS functionality for example?

No, but it's also not true that the only way to implement GPS is by
opening a full on command/packet interface between fat proprietary
firmware and custom user space (which may or may not be proprietary 
as well).

> >> 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.  
> 
> Uploading runtime firmware, with variations based on the runtime mode. 
> Flashing the onboard flash based on cryptographic keys.  Accessing 
> configuration data.  Accessing device logs.  Configuring device logs. 
> Synchronizing the device time reference to Linux local or remote time 
> sources.  Enabling debugging/performance hardware.  Getting software 
> diagnostic events.  Configuring redundancy hardware per workload. 
> Uploading new cryptographic keys.  Invalidating cryptographic keys. 
> Uploading factory test data and running factory tests.
> 
> Need more?

This conversation is going nowhere. Are you trying to say that creating
a common Linux API for those features is impossible and each vendor
should be allowed to add their own proprietary way?

This has been proven incorrect again and again, and Wi-Fi is a good
example.

You can do whatever you want for GPS etc. but don't come nowhere near
networking with this attitude please.

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Jeffrey Hugo]

On 12/1/2020 7:55 PM, Jakub Kicinski wrote:
> On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote:
>> On 12/1/2020 1:03 PM, 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.
>>
>> So a WLAN device is only ever allowed to do Wi-Fi?  It can't also have
>> GPS functionality for example?
> 
> No, but it's also not true that the only way to implement GPS is by
> opening a full on command/packet interface between fat proprietary
> firmware and custom user space (which may or may not be proprietary
> as well).

Funny, that exactly what the GPS "API" in the kernel is, although a bit 
limited to the specifics on the standardized GPS "sentences" and not 
covering implementation specific configuration.

> 
>>>> 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.
>>
>> Uploading runtime firmware, with variations based on the runtime mode.
>> Flashing the onboard flash based on cryptographic keys.  Accessing
>> configuration data.  Accessing device logs.  Configuring device logs.
>> Synchronizing the device time reference to Linux local or remote time
>> sources.  Enabling debugging/performance hardware.  Getting software
>> diagnostic events.  Configuring redundancy hardware per workload.
>> Uploading new cryptographic keys.  Invalidating cryptographic keys.
>> Uploading factory test data and running factory tests.
>>
>> Need more?
> 
> This conversation is going nowhere. Are you trying to say that creating
> a common Linux API for those features is impossible and each vendor
> should be allowed to add their own proprietary way?
> 
> This has been proven incorrect again and again, and Wi-Fi is a good
> example.
> 
> You can do whatever you want for GPS etc. but don't come nowhere near
> networking with this attitude please.
> 

No I'm saying (and Bjorn/Mani by the looks of things), that there is 
commonality in the core features - IP traffic, Wi-Fi, etc but then there 
are vendor specific things which are either things you don't actually 
want in the kernel, don't want the kernel doing, or have little 
commonality between vendors such that attempting to unify them gains you 
little to nothing.

Over in the networking space, I can see where standardization is plenty 
useful.

I can't speak for other vendors, but a "modem" or a "wlan" device from 
Qualcomm is not something that just provides one service.  They tend to 
provide dozens of different functionalities, some of those are 
"standardized" like wi-fi where common wi-fi interfaces are used. 
Others are unique to Qualcomm.

The point is "wlan device" is a superset of "wi-fi".  You seem to be 
equating them to be the same in a "shoot first, ask questions later" manner.

This series provides a way for userspace to talk to remote MHI "widgets" 
for usecases not covered elsewhere.  Those "widgets" just happen to 
commonly provide modem/wlan services, but ones that don't are not excluded.

Regarding not coming near networking, I'd like to remind you it was you 
that decided to come over here to the non-networking area and try to 
make this about networking.

-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Leon Romanovsky]

On Tue, Dec 01, 2020 at 09:59:53PM -0700, Jeffrey Hugo wrote:
> On 12/1/2020 7:55 PM, Jakub Kicinski wrote:
> > On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote:
> > > On 12/1/2020 1:03 PM, 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.
> > >
> > > So a WLAN device is only ever allowed to do Wi-Fi?  It can't also have
> > > GPS functionality for example?
> >
> > No, but it's also not true that the only way to implement GPS is by
> > opening a full on command/packet interface between fat proprietary
> > firmware and custom user space (which may or may not be proprietary
> > as well).
>
> Funny, that exactly what the GPS "API" in the kernel is, although a bit
> limited to the specifics on the standardized GPS "sentences" and not
> covering implementation specific configuration.
>
> >
> > > > > 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.
> > >
> > > Uploading runtime firmware, with variations based on the runtime mode.
> > > Flashing the onboard flash based on cryptographic keys.  Accessing
> > > configuration data.  Accessing device logs.  Configuring device logs.
> > > Synchronizing the device time reference to Linux local or remote time
> > > sources.  Enabling debugging/performance hardware.  Getting software
> > > diagnostic events.  Configuring redundancy hardware per workload.
> > > Uploading new cryptographic keys.  Invalidating cryptographic keys.
> > > Uploading factory test data and running factory tests.
> > >
> > > Need more?
> >
> > This conversation is going nowhere. Are you trying to say that creating
> > a common Linux API for those features is impossible and each vendor
> > should be allowed to add their own proprietary way?
> >
> > This has been proven incorrect again and again, and Wi-Fi is a good
> > example.
> >
> > You can do whatever you want for GPS etc. but don't come nowhere near
> > networking with this attitude please.
> >
>
> No I'm saying (and Bjorn/Mani by the looks of things), that there is
> commonality in the core features - IP traffic, Wi-Fi, etc but then there are
> vendor specific things which are either things you don't actually want in
> the kernel, don't want the kernel doing, or have little commonality between
> vendors such that attempting to unify them gains you little to nothing.
>
> Over in the networking space, I can see where standardization is plenty
> useful.
>
> I can't speak for other vendors, but a "modem" or a "wlan" device from
> Qualcomm is not something that just provides one service.  They tend to
> provide dozens of different functionalities, some of those are
> "standardized" like wi-fi where common wi-fi interfaces are used. Others are
> unique to Qualcomm.
>
> The point is "wlan device" is a superset of "wi-fi".  You seem to be
> equating them to be the same in a "shoot first, ask questions later" manner.
>
> This series provides a way for userspace to talk to remote MHI "widgets" for
> usecases not covered elsewhere.  Those "widgets" just happen to commonly
> provide modem/wlan services, but ones that don't are not excluded.
>
> Regarding not coming near networking, I'd like to remind you it was you that
> decided to come over here to the non-networking area and try to make this
> about networking.

Like it or not, but Jakub is absolutely right with his claim that
providing user-visible interfaces without any standardization is proven
as wrong.

Thanks

>
> --
> Jeffrey Hugo
> Qualcomm Technologies, Inc. is a member of the
> Code Aurora Forum, a Linux Foundation Collaborative Project.

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Manivannan Sadhasivam]

On Sun, Dec 06, 2020 at 10:33:02AM +0200, Leon Romanovsky wrote:
> On Tue, Dec 01, 2020 at 09:59:53PM -0700, Jeffrey Hugo wrote:
> > On 12/1/2020 7:55 PM, Jakub Kicinski wrote:
> > > On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote:
> > > > On 12/1/2020 1:03 PM, 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.
> > > > > > >

[...]

> Like it or not, but Jakub is absolutely right with his claim that
> providing user-visible interfaces without any standardization is proven
> as wrong.
> 

Everybody agrees with standardizing things but the problem is, the
standardization will only happen when more than one person implements the
same functionality.

The primary discussion is around the usage of chardev nodes for WLAN but
we made it clear that WLAN doesn't need this chardev node for working at
all. I agree that the commit message is a bit misleading and I hope that
Hemant will fix it in next revision.

Thanks,
Mani

> Thanks
> 
> >
> > --
> > Jeffrey Hugo
> > Qualcomm Technologies, Inc. is a member of the
> > Code Aurora Forum, a Linux Foundation Collaborative Project.

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Leon Romanovsky]

On Tue, Dec 08, 2020 at 10:29:27PM +0530, Manivannan Sadhasivam wrote:
> On Sun, Dec 06, 2020 at 10:33:02AM +0200, Leon Romanovsky wrote:
> > On Tue, Dec 01, 2020 at 09:59:53PM -0700, Jeffrey Hugo wrote:
> > > On 12/1/2020 7:55 PM, Jakub Kicinski wrote:
> > > > On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote:
> > > > > On 12/1/2020 1:03 PM, 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.
> > > > > > > >
>
> [...]
>
> > Like it or not, but Jakub is absolutely right with his claim that
> > providing user-visible interfaces without any standardization is proven
> > as wrong.
> >
>
> Everybody agrees with standardizing things but the problem is, the
> standardization will only happen when more than one person implements the
> same functionality.

From my experience in RDMA and netdev, I can't agree with both of your
statements. There are a lot of people who see standardization as a bad
thing. Also we are pushing even one person to make user visible interfaces
right from the beginning without relation to how wide it will be adopted
later.

Thanks

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Manivannan Sadhasivam]

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

Re: [PATCH v13 0/4] userspace MHI client interface driver

[Bjorn Andersson]

On Tue 01 Dec 13:29 CST 2020, 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.
> 

No, this allows exposing particular channels from any type of MHI
devices.

For modems there is a legacy control path that uses UCI. But data
traffic, (non-legacy) modem control signals and e.g the bearer of GPS
data uses in-kernel drivers that are already in place.

> Why do WLAN devices need to communicate with user space?

They normally don't, all WLAN operations are dealt with within the
kernel. The use case that comes to mind for UCI when it comes to WiFi
products is to avoid implementing the Qualcomm debug (diag) protocol in
the kernel.


As such I think saying that it can be used to communicate with modem or
WLAN devices is misleading. Because while it could be done, it is only
used for dealing with optional side-band services on such products - not
the actual WiFi and modem functionality.

Regards,
Bjorn