From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay3-d.mail.gandi.net (relay3-d.mail.gandi.net [217.70.183.195]) (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 85EF36D17; Mon, 5 May 2025 11:22:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746444176; cv=none; b=tvCpk4URv8aueV8kNj8GhdKdUste2cFpmRwAKBLuGUyS+Z7DFkpUw1Gq26IIH9RICEMmiOYT8qGROc0r17x+C4xwijeVzlJI7aFlCjHFUWj0+1SCVNEcpHdAQxjHO6xkopM2QdwSpjXmVgNgSpvT648bNJLkdQU7QKhVMr2t67M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746444176; c=relaxed/simple; bh=X7f/cj2HyCw5T24zVizPuI3ejjSC/I4KfwGIek8QsVE=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=o7YqcQRSwuFs7Zqfr8QgTGbN95iwsOlY/oQfHzLCob3KTR79CkYAn4SR2vWbek8m0Ryys/Iru9Ntk5fMTCoGQXYOApNQ37TvYrLWEGPZM3gQc80KPvzfZSJR3ChgMxRF9cwgE66sD1ku0dawO3jqHZmngoLgT+0+xYY3IG3XqGc= ARC-Authentication-Results:i=1; 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bh=BjQD6/4ZASrQpmuxOr/8hzy+9Fqcd4Ygjsti998CXt4=; b=dngknP3B2/vVmzmsbaZxjuZILonwn1c7s6KP+leUH2BrK41WmAJ3r2zE0ccLwPB4wpBLzT JUXW0vkq4VwyeHl3/ucynqrRsnTi85cb3eztsVpv+p4OzzL17kaM2dsaLTtnLxkh6Xc/ON clU6u/QuPeMjTz7YdipPU6gbqmxfgQX+ipKfIVjFyyyFkCHwf5ParQX1yatiTBo/obF9nC Ou5RRD21tdkElQ9rvlhNgLylZpNhJjsmny3GfYwbTSQvCLifHN++17o8zo67wunEZCHZgt JgH0CwAwK+UOKoPI5wri7ICjZoPWrJC2d36EjvwpV1hPU+SCbPyP6aC0i+8Xlg== Date: Mon, 5 May 2025 13:22:47 +0200 From: Luca Ceresoli To: Cosmin Tanislav Cc: Tomi Valkeinen , Wolfram Sang , Mauro Carvalho Chehab , Romain Gantois , Arnd Bergmann , Greg Kroah-Hartman , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org Subject: Re: [PATCH v4 3/9] i2c: atr: split up i2c_atr_get_mapping_by_addr() Message-ID: <20250505132247.3ba8af2a@booty> In-Reply-To: References: <20250428102516.933571-1-demonsingur@gmail.com> <20250428102516.933571-4-demonsingur@gmail.com> <20250430163307.528671a8@booty> Organization: Bootlin X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgddvkedtleeiucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuifetpfffkfdpucggtfgfnhhsuhgsshgtrhhisggvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeffhffvvefukfgjfhhoofggtgfgsehtjeertdertddvnecuhfhrohhmpefnuhgtrgcuvegvrhgvshholhhiuceolhhutggrrdgtvghrvghsohhlihessghoohhtlhhinhdrtghomheqnecuggftrfgrthhtvghrnhepgeelffefgfehhfdtvdefueefieevkefggfelkeeiudetkeektedvhedukefgvddvnecuffhomhgrihhnpegsohhothhlihhnrdgtohhmnecukfhppedvrgdtvdemieejtdemvddtvddtmegvrgdtudemsggvgedumeelhegvjeemfeegfeemledufegvnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepvdgrtddvmeeijedtmedvtddvtdemvggrtddumegsvgegudemleehvgejmeefgeefmeeludefvgdphhgvlhhopegsohhothihpdhmrghilhhfrhhomheplhhutggrrdgtvghrvghsohhlihessghoohhtlhhinhdrtghomhdpnhgspghrtghpthhtohepuddtpdhrtghpthhtohepuggvmhhonhhsihhnghhurhesghhmrghilhdrtghomhdprhgtphhtthhopehtohhmihdrvhgrlhhkvghinhgvnhesihguvggrshhonhgsohgrrhgurdgtohhmpdhrtghpthhtohepfihsrgdorhgvnhgvs hgrshesshgrnhhgqdgvnhhgihhnvggvrhhinhhgrdgtohhmpdhrtghpthhtohepmhgthhgvhhgrsgeskhgvrhhnvghlrdhorhhgpdhrtghpthhtoheprhhomhgrihhnrdhgrghnthhoihhssegsohhothhlihhnrdgtohhmpdhrtghpthhtoheprghrnhgusegrrhhnuggsrdguvgdprhgtphhtthhopehgrhgvghhkhheslhhinhhugihfohhunhgurghtihhonhdrohhrghdprhgtphhtthhopehlihhnuhigqdhivdgtsehvghgvrhdrkhgvrhhnvghlrdhorhhg X-GND-Sasl: luca.ceresoli@bootlin.com On Mon, 5 May 2025 13:26:54 +0300 Cosmin Tanislav wrote: > On 4/30/25 5:33 PM, Luca Ceresoli wrote: > > On Mon, 28 Apr 2025 13:25:08 +0300 > > Cosmin Tanislav wrote: > > > >> The i2c_atr_get_mapping_by_addr() function handles three separate > >> usecases: finding an existing mapping, creating a new mapping, or > >> replacing an existing mapping if a new mapping cannot be created > >> because there aren't enough aliases available. > >> > >> Split up the function into three different functions handling its > >> individual usecases to prepare for better usage of each one. > >> > >> Signed-off-by: Cosmin Tanislav > > > > This function has become quite complex over time, so this looks like a > > good cleanup by itself even not counting the advantages coming with the > > following patches. > > > > I have only one small remark, see below. > > > >> diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c > >> index 939fb95fe781..184c57c31e60 100644 > >> --- a/drivers/i2c/i2c-atr.c > >> +++ b/drivers/i2c/i2c-atr.c > >> @@ -239,9 +239,23 @@ static void i2c_atr_release_alias(struct i2c_atr_alias_pool *alias_pool, u16 ali > >> spin_unlock(&alias_pool->lock); > >> } > >> > >> -/* Must be called with alias_pairs_lock held */ > >> static struct i2c_atr_alias_pair * > >> -i2c_atr_get_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr) > >> +i2c_atr_find_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr) > >> +{ > >> + struct i2c_atr_alias_pair *c2a; > >> + > >> + lockdep_assert_held(&chan->alias_pairs_lock); > >> + > >> + list_for_each_entry(c2a, &chan->alias_pairs, node) { > >> + if (c2a->addr == addr) > >> + return c2a; > >> + } > >> + > >> + return NULL; > >> +} > >> + > >> +static struct i2c_atr_alias_pair * > >> +i2c_atr_replace_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr) > >> { > >> struct i2c_atr *atr = chan->atr; > >> struct i2c_atr_alias_pair *c2a; > >> @@ -254,41 +268,57 @@ i2c_atr_get_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr) > >> > >> alias_pairs = &chan->alias_pairs; > >> > >> - list_for_each_entry(c2a, alias_pairs, node) { > >> - if (c2a->addr == addr) > >> - return c2a; > >> + if (unlikely(list_empty(alias_pairs))) > >> + return NULL; > >> + > >> + list_for_each_entry_reverse(c2a, alias_pairs, node) { > >> + if (!c2a->fixed) { > >> + found = true; > >> + break; > >> + } > >> } > >> > >> + if (!found) > >> + return NULL; > >> + > >> + atr->ops->detach_addr(atr, chan->chan_id, c2a->addr); > >> + c2a->addr = addr; > >> + > >> + list_move(&c2a->node, alias_pairs); > >> + > >> + alias = c2a->alias; > >> + > >> + ret = atr->ops->attach_addr(atr, chan->chan_id, c2a->addr, c2a->alias); > >> + if (ret) { > >> + dev_err(atr->dev, "failed to attach 0x%02x on channel %d: err %d\n", > >> + addr, chan->chan_id, ret); > >> + i2c_atr_destroy_c2a(&c2a); > >> + i2c_atr_release_alias(chan->alias_pool, alias); > >> + return NULL; > >> + } > >> + > >> + return c2a; > >> +} > >> + > >> +static struct i2c_atr_alias_pair * > >> +i2c_atr_create_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr) > > > > I would move the _create function before the _replace one, because > > that's the logical order in which they are called. > > > > Sadly the diff actually becomes bigger by doing this. > before: 78 insertions(+), 32 deletions(-) > after: 84 insertions(+), 38 deletions(-) The diff size is not at all the primary goal. I just epected it would reduce, but OK, it does not matter. > If we were to put things in a logical order then should we put _find() > after create(), or after replace()? There's no specific order in that > case. I think we should keep things as-is as it matches the previous > branches of the code, just split into separate functions. Definitely find, create, replace. It's the order in which they are executed, as clearly visible i2c_atr_get_mapping_by_addr(). It's also the logical order in the old code, even though it is visually looking reverse: [old] i2c_atr_find_mapping_by_addr(): - list_for_each_entry() # then new _find - i2c_atr_reserve_alias() # this is the 1st half of the new _create - if (success) - i2c_atr_create_c2a() # 2nd half of the new _create - else - list_for_each_entry_reverse... atr->ops->detach_addr... list_move... # the new _replace This has of course no impact on the actual executed code, it's just a matter of code organization which I believe should be intuitive when doable with a small effort. Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com