Linux-USB Archive on
 help / color / Atom feed
From: Heikki Krogerus <>
To: Guenter Roeck <>
Cc: Hans de Goede <>,
Subject: Re: [PATCH 1/7] usb: typec: Copy everything from struct typec_capability during registration
Date: Wed, 2 Oct 2019 22:16:59 +0300
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, Oct 02, 2019 at 07:06:55PM +0300, Heikki Krogerus wrote:
> This is a bit off topic, but that attribute file is really horrible.
> Right now there is no way to know the actual capability of the
> port in user space. If something changes a DRP port into sink or
> source, there is no way to know after that that the port is actually
> DRP capable.

That statement is not correct. I'm sorry. I don't know why did I put
it that way.

I wanted to say that now the userpsace is forced to keep track of a
specific sysfs file in order to be sure of the currently supported
role, That alone is wrong, but there is no way to guarantee that
one day we would not need to support another capability in a similar
fashion, and that would mean another sysfs file, and we just forced
the userspace to be modified. The capabilities of the port really need
to be static.

We can handle the capability changes like I propose below without
affecting the userspace.

> So that ABI is "buggy", but even without the problem, I still really
> think that allowing the capabilities to be changed like that in
> general is completely wrong. I don't have a problem with changing the
> capabilities, but IMO it should be handled at one level higher, at the
> controller device level. If the capabilities of a port need to be
> changed, the old port should be removed, and a new with the new
> capabilities registered. That is the only way to handle it without
> making things unnecessarily difficult for the user space.
> I'm pretty sure that that was my counter proposal already at the time
> when the attribute file was introduced, but I don't remember why
> wasn't it accepted at the time? My protest against adding that
> attribute file was in any case ignored :-(. In any case, my plan was
> to later propose a new sysfs group that we offer to the parent
> controller devices instead assigning it to the port devices, and that
> group is meant to allow port capability changes the way I explained
> above. Unless of course you are against it?
> thanks,
> -- 
> heikki


  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-01  9:48 [PATCH 0/7] usb: typec: Small API improvement Heikki Krogerus
2019-10-01  9:48 ` [PATCH 1/7] usb: typec: Copy everything from struct typec_capability during registration Heikki Krogerus
2019-10-01 13:08   ` Guenter Roeck
2019-10-02 16:06     ` Heikki Krogerus
2019-10-02 16:36       ` Guenter Roeck
2019-10-02 18:29         ` Heikki Krogerus
2019-10-03  3:45           ` Guenter Roeck
2019-10-03  8:03             ` Heikki Krogerus
2019-10-02 19:16       ` Heikki Krogerus [this message]
2019-10-03  3:51         ` Guenter Roeck
2019-10-03 13:29           ` Heikki Krogerus
2019-10-01  9:48 ` [PATCH 2/7] usb: typec: Introduce typec_get_drvdata() Heikki Krogerus
2019-10-01  9:48 ` [PATCH 3/7] usb: typec: Separate the operations vector Heikki Krogerus
2019-10-01 13:22   ` Guenter Roeck
2019-10-04  8:45     ` Heikki Krogerus
2019-10-01  9:48 ` [PATCH 4/7] usb: typec: tcpm: Start using struct typec_operations Heikki Krogerus
2019-10-01 13:30   ` Guenter Roeck
2019-10-04  8:46     ` Heikki Krogerus
2019-10-01  9:48 ` [PATCH 5/7] usb: typec: tps6598x: " Heikki Krogerus
2019-10-01 13:34   ` Guenter Roeck
2019-10-01 13:35   ` Guenter Roeck
2019-10-04  8:49     ` Heikki Krogerus
2019-10-01  9:48 ` [PATCH 6/7] usb: typec: ucsi: " Heikki Krogerus
2019-10-01 13:35   ` Guenter Roeck
2019-10-01  9:48 ` [PATCH 7/7] usb: typec: Remove the callback members from struct typec_capability Heikki Krogerus
2019-10-01 13:37   ` Guenter Roeck

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-USB Archive on

Archives are clonable:
	git clone --mirror linux-usb/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-usb linux-usb/ \
	public-inbox-index linux-usb

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone