From: "David Nyström" <david.nystrom@est.tech>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: "David Nyström" <david.nystrom@est.tech>,
"Alexandre Belloni" <alexandre.belloni@bootlin.com>,
"Frank Li" <Frank.Li@nxp.com>,
linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i3c: master: Add WO sysfs option to re-DDA bus.
Date: Thu, 22 Jan 2026 16:47:23 +0100 (CET) [thread overview]
Message-ID: <6b15a03c-57ae-021a-581c-4f83e58842e8@est.tech> (raw)
In-Reply-To: <aXIdsGgHQQPKy4Ok@shikoro>
[-- Attachment #1: Type: text/plain, Size: 851 bytes --]
On Thu, 22 Jan 2026, Wolfram Sang wrote:
> On Thu, Jan 22, 2026 at 12:36:30PM +0100, David Nyström wrote:
>> Add ability to rescan the i3c bus from userspace, i.e. provoke a DDA.
>
> Your are describing what you do but what is missing is why you want the
> change. What is the use case?
The usecase would be an i3cdev userspace driver for a device with
broken hotjoin support.
The device requires FW loading(userspace framework) before it will respond
to DAA, and is thus not registered during initial bus probe.
I guess a similiar problem would apply if hot-join is bus disabled
via sysfs, and resume hook DDA runs before i3c devices are powered up properly.
A bit of a niche usecase, I know.
I found it to be usable though, but perhaps this is better placed in
debugfs in case its too much of an eyesore for the stable ABI.
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WARNING: multiple messages have this Message-ID (diff)
From: "David Nyström" <david.nystrom@est.tech>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: "David Nyström" <david.nystrom@est.tech>,
"Alexandre Belloni" <alexandre.belloni@bootlin.com>,
"Frank Li" <Frank.Li@nxp.com>,
linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i3c: master: Add WO sysfs option to re-DDA bus.
Date: Thu, 22 Jan 2026 16:47:23 +0100 (CET) [thread overview]
Message-ID: <6b15a03c-57ae-021a-581c-4f83e58842e8@est.tech> (raw)
In-Reply-To: <aXIdsGgHQQPKy4Ok@shikoro>
[-- Attachment #1: Type: text/plain, Size: 851 bytes --]
On Thu, 22 Jan 2026, Wolfram Sang wrote:
> On Thu, Jan 22, 2026 at 12:36:30PM +0100, David Nyström wrote:
>> Add ability to rescan the i3c bus from userspace, i.e. provoke a DDA.
>
> Your are describing what you do but what is missing is why you want the
> change. What is the use case?
The usecase would be an i3cdev userspace driver for a device with
broken hotjoin support.
The device requires FW loading(userspace framework) before it will respond
to DAA, and is thus not registered during initial bus probe.
I guess a similiar problem would apply if hot-join is bus disabled
via sysfs, and resume hook DDA runs before i3c devices are powered up properly.
A bit of a niche usecase, I know.
I found it to be usable though, but perhaps this is better placed in
debugfs in case its too much of an eyesore for the stable ABI.
next prev parent reply other threads:[~2026-03-11 22:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-22 11:36 [PATCH] i3c: master: Add WO sysfs option to re-DDA bus David Nyström
2026-01-22 11:36 ` David Nyström
2026-01-22 12:53 ` Wolfram Sang
2026-01-22 12:53 ` Wolfram Sang
2026-01-22 15:47 ` David Nyström [this message]
2026-01-22 15:47 ` David Nyström
2026-01-22 16:00 ` Frank Li
2026-01-22 16:00 ` Frank Li
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