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Fri, 17 Jul 2020 04:06:11 -0700 (PDT) Date: Fri, 17 Jul 2020 20:06:10 +0900 From: Sergey Senozhatsky To: Bingbu Cao Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, sakari.ailus@linux.intel.com, srinivas.kandagatla@linaro.org, tfiga@chromium.org, bingbu.cao@linux.intel.com Subject: Re: [PATCH] media: ov2740: add NVMEM interface to read customized OTP data Message-ID: <20200717110610.GA3297952@google.com> References: <1591954922-14006-1-git-send-email-bingbu.cao@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1591954922-14006-1-git-send-email-bingbu.cao@intel.com> Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On (20/06/12 17:42), Bingbu Cao wrote: > > +static int ov2740_nvmem_read(void *priv, unsigned int off, void *val, > + size_t count) > +{ > + struct nvm_data *nvm = priv; > + > + memcpy(val, nvm->nvm_buffer + off, count); > + > + return 0; > +} > + > +static int ov2740_register_nvmem(struct i2c_client *client) > +{ > + struct nvm_data *nvm; > + struct regmap_config regmap_config = { }; > + struct nvmem_config nvmem_config = { }; > + struct regmap *regmap; > + struct device *dev = &client->dev; > + int ret = 0; > + > + nvm = devm_kzalloc(dev, sizeof(*nvm), GFP_KERNEL); > + if (!nvm) > + return -ENOMEM; > + > + regmap_config.val_bits = 8; > + regmap_config.reg_bits = 16; > + regmap_config.disable_locking = true; > + regmap = devm_regmap_init_i2c(client, ®map_config); > + if (IS_ERR(regmap)) > + return PTR_ERR(regmap); > + > + nvm->regmap = regmap; > + > + nvmem_config.name = dev_name(dev); > + nvmem_config.dev = dev; > + nvmem_config.read_only = true; > + nvmem_config.root_only = true; > + nvmem_config.owner = THIS_MODULE; > + nvmem_config.compat = true; > + nvmem_config.base_dev = dev; > + nvmem_config.reg_read = ov2740_nvmem_read; > + nvmem_config.reg_write = NULL; > + nvmem_config.priv = nvm; > + nvmem_config.stride = 1; > + nvmem_config.word_size = 1; > + nvmem_config.size = CUSTOMER_USE_OTP_SIZE; > + > + nvm->nvmem = devm_nvmem_register(dev, &nvmem_config); > + if (IS_ERR(nvm->nvmem)) > + return PTR_ERR(nvm->nvmem); This registers the NVM device, but the underlying structure is not completely initialized yet. For instance, the ->num_buffer, which ->reg_read() uses as buffer base address, is still NULL at this point. I'd be more comfortable if we first fully setup/prepare everything and only then register the device. > + > + nvm->nvm_buffer = devm_kzalloc(dev, CUSTOMER_USE_OTP_SIZE, GFP_KERNEL); > + if (!nvm->nvm_buffer) > + return -ENOMEM; If this allocation fails, we return the error, which is handler as dev_err() only, and keep everting as is. So any attempt of ->req_read() will effectively do memcpy(val, NULL + off, count); > + ret = ov2740_load_otp_data(client, nvm); > + if (ret) > + dev_err(dev, "failed to load OTP data, ret %d\n", ret); > + > + return ret; > +} If this step fails, the NVM device is still registered and available and we still can call ->req_read(). Is this correct? Do we need to have an "error out" path there and unregister the NVM device? > static int ov2740_probe(struct i2c_client *client) > { > struct ov2740 *ov2740; > @@ -964,6 +1105,10 @@ static int ov2740_probe(struct i2c_client *client) > goto probe_error_media_entity_cleanup; > } > > + ret = ov2740_register_nvmem(client); > + if (ret) > + dev_err(&client->dev, "register nvmem failed, ret %d\n", ret); > + Either this better be a fatal error, or we need to have an error-out rollback/cleanup in ov2740_register_nvmem(). > /* > * Device is already turned on by i2c-core with ACPI domain PM. > * Enable runtime PM and turn off the device. -ss