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[92.233.226.227]) by smtp.googlemail.com with ESMTPSA id n125sm3703525wmf.30.2021.01.26.06.03.30 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Jan 2021 06:03:30 -0800 (PST) Subject: Re: [RFC PATCH 1/2] ASoC: soc-component: add snd_soc_component_read/write_field() To: Mark Brown Cc: lgirdwood@gmail.com, alsa-devel@alsa-project.org, perex@perex.cz, tiwai@suse.com, linux-kernel@vger.kernel.org, vkoul@kernel.org References: <20210126122020.19735-1-srinivas.kandagatla@linaro.org> <20210126133612.GB4839@sirena.org.uk> From: Srinivas Kandagatla Message-ID: <6816a9fe-9b71-6a39-485e-1b6ce2b732ed@linaro.org> Date: Tue, 26 Jan 2021 14:03:29 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20210126133612.GB4839@sirena.org.uk> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/01/2021 13:36, Mark Brown wrote: > On Tue, Jan 26, 2021 at 12:20:19PM +0000, Srinivas Kandagatla wrote: > >> +#define __soc_component_field_shift(x) (__builtin_ffs(x) - 1) > > Why not have this be a static inline? Sure, that makes it even better to validate the mask aswell! > >> +unsigned int snd_soc_component_read_field(struct snd_soc_component *component, >> + unsigned int reg, unsigned int mask) >> +{ >> + unsigned int val; >> + >> + mutex_lock(&component->io_mutex); >> + val = soc_component_read_no_lock(component, reg); >> + if (mask) >> + val = (val & mask) >> __soc_component_field_shift(mask); > > I don't understand why this is open coding the locking when it's just a > simple read and then shift? I agree! something like this should be good I guess: unsigned int snd_soc_component_read_field(...) { unsigned int val; val = snd_soc_component_read(component, reg); val = (val & mask) >> __soc_component_field_shift(mask); return val; } > >> + mutex_lock(&component->io_mutex); >> + >> + old = soc_component_read_no_lock(component, reg); >> + >> + val = val << __soc_component_field_shift(mask); >> + >> + new = (old & ~mask) | (val & mask); >> + >> + change = old != new; >> + if (change) >> + ret = soc_component_write_no_lock(component, reg, new); >> + >> + mutex_unlock(&component->io_mutex); > > This needs the lock as it's a read/modify/write but could also be > implemented in terms of the existing update_bits() operation rather than > open coding it. True!, we could simplify this to : int snd_soc_component_write_field(struct snd_soc_component *component, unsigned int reg, unsigned int mask, unsigned int val) { val = (val << __soc_component_field_shift(mask)) & mask; return snd_soc_component_update_bits(component, reg, mask, val); } Does that look okay to you? --srini >