From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 24018208D7D for ; Wed, 16 Oct 2024 13:18:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729084716; cv=none; b=pA5c8bnU2pW/iHQFlkmGpZ2SWnMmr4hMS6JV7N1IfHdkvGSZiaFsh5GFiledjv+pBRFXQEIEKcAJhJkoKgDWoA5lkyvuJsIrxxuZJcn031tvB5jCjd0KOP9pU9e6bW2RB4lY0DKEY89Uz+XutDqhGkumW33wnzXQFXNLjKYEpTs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729084716; c=relaxed/simple; bh=Ei04/y7E+9GEINyDxafGA/mkjtrWrbFV5lAkYjh0DQQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tEsBIUqmvSrr3Dnr/YQzP4qjH3xYYe8MIqbEHRx7Z/2q3g3/WTyoJd+SZl8ITF7iWNaihcmP51TLTqTCo9rR1E7LXejxTqPzOX4wzM3bjId5iq7jdGjv4kV3B1vFPncshVeCskFoOZdrvpt6Y8R/AjFNpvsDMo/sgQbsUf4dgHs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mycDx9OT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mycDx9OT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B93BDC4CEC5; Wed, 16 Oct 2024 13:18:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729084715; bh=Ei04/y7E+9GEINyDxafGA/mkjtrWrbFV5lAkYjh0DQQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mycDx9OTDHRJ5FvjAxCOhWlYOC+2328tkRSCNO1lqE/9UBf4R+IFRiw/K0GHwl9ON JPTrUR17Rf5OT8KSpdWY1vPlkNiinEG0KKdeai7cuKyH1b3yVI/qKL1Q33ELUsT3uC E5awGRa62YfkZKdrOQlbnf3rDrR6PZvCNBAmArIJk/ccnQj6I6vgR236LYr7/2YwW2 hbpBRB2msDZR99L7Wbsb0QpW1QTkjxFk290WEQOYLwJnhI9TGDummXNJut2IyBjkbR OWTPxLQnSA4JniqVfjCTfxcIFfqDujCB1wd62UIw0sYaQvBnp7etM5XL/v8+tu7C6Y F8TDvHPty0ZXA== Date: Wed, 16 Oct 2024 14:18:32 +0100 From: Lee Jones To: Matthias Schiffer Cc: linux@ew.tq-group.com, linux-kernel@vger.kernel.org, Gregor Herburger Subject: Re: [PATCH v4 5/5] mfd: tqmx86: add I2C IRQ support Message-ID: <20241016131832.GC1152434@google.com> References: <20241015113841.GH8348@google.com> <8fbae19e7e85a8fc8d6f9738155ec8fe44e63061.camel@ew.tq-group.com> <20241016130715.GA1152434@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, 16 Oct 2024, Matthias Schiffer wrote: > On Wed, 2024-10-16 at 14:07 +0100, Lee Jones wrote: > > > > On Wed, 16 Oct 2024, Matthias Schiffer wrote: > > > > > On Tue, 2024-10-15 at 12:38 +0100, Lee Jones wrote: > > > > > > > > On Mon, 07 Oct 2024, Matthias Schiffer wrote: > > > > > > > > > From: Gregor Herburger > > > > > > > > > > The i2c-ocores controller can run in interrupt mode on tqmx86 modules. > > > > > Add module parameter to allow configuring the IRQ number, similar to the > > > > > handling of the GPIO IRQ. > > > > > > > > > > Signed-off-by: Gregor Herburger > > > > > Signed-off-by: Matthias Schiffer > > > > > --- > > > > > > > > > > v2: improve module parameter description (was patch 4/4) > > > > > v3: replace IRQ 0 resource with an empty placeholder to simplify error handling > > > > > v4: no changes > > > > > > > > > > drivers/mfd/tqmx86.c | 20 +++++++++++++++++++- > > > > > 1 file changed, 19 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/mfd/tqmx86.c b/drivers/mfd/tqmx86.c > > > > > index e444fcd2a3e9d..057d035b71d33 100644 > > > > > --- a/drivers/mfd/tqmx86.c > > > > > +++ b/drivers/mfd/tqmx86.c > > > > > @@ -50,6 +50,7 @@ > > > > > #define TQMX86_REG_IO_EXT_INT_9 2 > > > > > #define TQMX86_REG_IO_EXT_INT_12 3 > > > > > #define TQMX86_REG_IO_EXT_INT_MASK 0x3 > > > > > +#define TQMX86_REG_IO_EXT_INT_I2C_SHIFT 0 > > > > > #define TQMX86_REG_IO_EXT_INT_GPIO_SHIFT 4 > > > > > #define TQMX86_REG_SAUC 0x17 > > > > > > > > > > @@ -60,7 +61,16 @@ static uint gpio_irq; > > > > > module_param(gpio_irq, uint, 0); > > > > > MODULE_PARM_DESC(gpio_irq, "GPIO IRQ number (valid parameters: 7, 9, 12)"); > > > > > > > > > > -static const struct resource tqmx_i2c_soft_resources[] = { > > > > > +static uint i2c_irq; > > > > > +module_param(i2c_irq, uint, 0); > > > > > +MODULE_PARM_DESC(i2c_irq, "I2C IRQ number (valid parameters: 7, 9, 12)"); > > > > > + > > > > > +static struct resource tqmx_i2c_soft_resources[] = { > > > > > + /* > > > > > + * Placeholder for IRQ resource - must come first to be filled in by the > > > > > + * probe function. > > > > > + */ > > > > > + {}, > > > > > > > > Having a NULLed entry in the first slot doesn't sit well with me at all. > > > > > > > > In order for us to avoid wasting memory, it would be better to place the > > > > entry at the end of the array with a blank entry: > > > > > > > > DEFINE_RES_IRQ(0), > > > > > > > > Later comes the matching code which updates the 0 value to something sane. > > > > > > > > Before you call to the add the devices, check to see if the value has > > > > changed. If it hasn't, deprecate num_resources, effectively masking the > > > > last entry in the array. Then when platform_device_add_resources() > > > > comes to duplicate the array, it will only copy the relevant entries. > > > > > > I chose my current solution because it resulted in more simple and maintainable code: > > > > > > - No dynamic array access, the IRQ resource is always written to index 0 > > > > Which is fragile (even with the comment). If you're going to directly > > index array elements, please do so with a unique identifier rather than > > relying on it happening to reside in the first. > > > > > - No surprises regarding num_resources, it is always equal to ARRAY_SIZE(resources) > > > > No surprises, but sometimes it's incorrect. > > > > > It also allowed to make all mfd_cell const; to make num_resources modifyable, either the const would > > > need to be removed, or each mfd_cell would need to be copied to a stack variable in the probe > > > function. > > > > > > In my opinion, these benefits outweigh the 2*64 bytes saved for the additional resources allocated > > > by platform_device_add_resources() - and 128 bytes doesn't seem significant at all, in particular > > > considering that this driver is used on x86_64 only. > > > > But doesn't outweigh my disliking for placing a NULL element at the > > start of the array. If you _must_ do something like this, please place > > it at the end of the array. > > > > Ok, will move the placeholder to the end, and access it using a defined index instead of 0. I would > still prefer to keep num_resources constant instead of adjusting it. Does this sound acceptable to > you? It would allow me to sleep at night, yes. :) -- Lee Jones [李琼斯]