From: Oliver Neukum <oneukum@suse.com>
To: "H. Peter Anvin" <hpa@zytor.com>, Oliver Neukum <oneukum@suse.com>
Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
gregkh@linuxfoundation.org, Jiri Slaby <jirislaby@kernel.org>,
linux-serial@vger.kernel.org
Subject: Re: USB cdc-acm driver: break and command
Date: Thu, 17 Jul 2025 13:28:05 +0200 [thread overview]
Message-ID: <c9d07302-37f0-4f0d-8669-094aa6fc2450@suse.com> (raw)
In-Reply-To: <f979468c-434a-43e9-8c50-8e92188abc11@zytor.com>
On 16.07.25 19:49, H. Peter Anvin wrote:
> On 2025-07-16 09:17, Oliver Neukum wrote:
>> Understood. It still seems dirty to me. If you want to send strings to a
>> device
>> the proper way is to use a device node and write().
>>
>
> There is definitely something to be said for that; or at least a file
> descriptor. We do have cases in the kernel -- notably opening the pts
> corresponding to a ptmx file descriptor -- that do that sort of
> "auxiliary open" kind of thing.
>
> The big question is how that interacts with the rest of the ACM driver,
> as well as all the lifetime issues you mentioned elsewhere.
It would seem to me that CDC already has something very similar in form
of CDC-WDM. If acm_probe() can call tty_port_register_device(), it can also
register a secondary character device. Or are you worried about how to tell
user space which devices belong together?
Regards
Oliver
prev parent reply other threads:[~2025-07-17 11:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-15 21:00 USB cdc-acm driver: break and command H. Peter Anvin
2025-07-16 6:58 ` Greg KH
2025-07-16 8:29 ` Oliver Neukum
2025-07-16 15:06 ` H. Peter Anvin
2025-07-16 16:17 ` Oliver Neukum
2025-07-16 17:30 ` H. Peter Anvin
2025-07-17 11:32 ` Oliver Neukum
2025-07-16 17:49 ` H. Peter Anvin
2025-07-17 11:28 ` Oliver Neukum [this message]
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