From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-p-202.mailbox.org (mout-p-202.mailbox.org [80.241.56.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C9ACC1A238F; Wed, 21 May 2025 18:36:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747852588; cv=none; b=kzO18I2fm3svd4pJ8404ji4bF+Szn6ypISH9CxngfyOvEip4yTUQyknpewCTQNg1PoG2raFrx4Sol2L4fd9lT3zCnRjw6gq4BBQiUxkY0rUvm555D9zjosqLLPc3MKPdnqdWxThHtULy2DntCg/7TrV0L1vD3PhVHF0yVAPQ5Fk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747852588; c=relaxed/simple; bh=4pF/fnEt73KK2G+WRSbc7QaKThEjnl0yHnYizDARC00=; h=Mime-Version:Content-Type:Date:Message-Id:To:Cc:Subject:From: References:In-Reply-To; b=T8uk7FpiJsWjdZ8esxv/FaNXJ0qCwoQvVT1qejn45VqWlT9SbInBkxtpIfND/saKuqfiDh58TyeCkaxdruX6jsf2j1Is/pTH3V8XSJqqI9hf14vdbFckhx54s4HfJD5rHb5oF6yx8ePsjF0BQGio1cbHux3w6n22bOosBcIrpMc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=buenzli.dev; spf=pass smtp.mailfrom=buenzli.dev; arc=none smtp.client-ip=80.241.56.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=buenzli.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=buenzli.dev Received: from smtp2.mailbox.org (smtp2.mailbox.org [10.196.197.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-202.mailbox.org (Postfix) with ESMTPS id 4b2g9Y1Y4bz9tBD; Wed, 21 May 2025 20:36:17 +0200 (CEST) Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 21 May 2025 20:36:10 +0200 Message-Id: To: "Greg Kroah-Hartman" Cc: "Rob Herring" , "Saravana Kannan" , "Miguel Ojeda" , "Alex Gaynor" , "Boqun Feng" , "Gary Guo" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Alice Ryhl" , "Trevor Gross" , "Danilo Krummrich" , "Rafael J. Wysocki" , "Dirk Behme" , , , Subject: Re: [PATCH v5 4/9] rust: device: Enable printing fwnode name and path From: "Remo Senekowitsch" References: <20250520200024.268655-1-remo@buenzli.dev> <20250520200024.268655-5-remo@buenzli.dev> <2025052153-steadier-bargraph-e81a@gregkh> <2025052116-gem-blend-2585@gregkh> In-Reply-To: <2025052116-gem-blend-2585@gregkh> On Wed May 21, 2025 at 6:58 PM CEST, Greg Kroah-Hartman wrote: > On Wed, May 21, 2025 at 03:03:07PM +0200, Remo Senekowitsch wrote: >> On Wed May 21, 2025 at 2:02 PM CEST, Greg Kroah-Hartman wrote: >> > On Tue, May 20, 2025 at 10:00:19PM +0200, Remo Senekowitsch wrote: >> >> Add two new public methods `display_name` and `display_path` to >> >> `FwNode`. They can be used by driver authors for logging purposes. In >> >> addition, they will be used by core property abstractions for automat= ic >> >> logging, for example when a driver attempts to read a required but >> >> missing property. >> >>=20 >> >> Signed-off-by: Remo Senekowitsch >> >> --- >> >> rust/kernel/device/property.rs | 72 ++++++++++++++++++++++++++++++++= ++ >> >> 1 file changed, 72 insertions(+) >> >>=20 >> >> diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/prop= erty.rs >> >> index 70593343bd811..6ccc7947f9c31 100644 >> >> --- a/rust/kernel/device/property.rs >> >> +++ b/rust/kernel/device/property.rs >> >> @@ -32,6 +32,78 @@ pub(crate) fn as_raw(&self) -> *mut bindings::fwno= de_handle { >> >> self.0.get() >> >> } >> >> =20 >> >> + /// Returns an object that implements [`Display`](core::fmt::Dis= play) for >> >> + /// printing the name of a node. >> >> + pub fn display_name(&self) -> impl core::fmt::Display + '_ { >> >> + struct FwNodeDisplayName<'a>(&'a FwNode); >> >> + >> >> + impl core::fmt::Display for FwNodeDisplayName<'_> { >> >> + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core:= :fmt::Result { >> >> + // SAFETY: self is valid by its type invariant >> >> + let name =3D unsafe { bindings::fwnode_get_name(self= .0.as_raw()) }; >> >> + if name.is_null() { >> >> + return Ok(()); >> > >> > So if there is no name, you are returning Ok()? Are you sure that's o= k >> > to do? What will the result of the string look like then? >>=20 >> In that case we're not writing anything to the formatter, which is >> equivalent to an empty string. `Ok(())` means that writing succeeded. >>=20 >> I assumed that a valid node would always have a name. And we're >> guaranteed to have a valid node. So I assumed this case would never >> happen and didn't think too hard about it. But even if a valid node has >> not name, empty string is probably the correct thing, right? > > I don't know what this "name" is used for. An empty string might not be > what you want to use here, given that you could be naming something > based on it, right? fwnode_get_name() is used for many things, > including the detection if a name is not present at all, and if not, > then the code needs to clean up and abort. > > So what exactly are you going to be using this for? Valid question... I'm not using it for anything. I was trying to match the C API which has capabilities to print a fwnode's name and full path. I think the format specifiers are %pfwP and %pfwf if I'm reading the source correctly. It also looks to me like the C API for printing fwnode names does the same thing - print nothing if the name is null. [1] [2] [1] https://elixir.bootlin.com/linux/v6.14.7/source/lib/vsprintf.c#L2242 [2] https://elixir.bootlin.com/linux/v6.14.7/source/lib/vsprintf.c#L711