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[84.106.84.65]) by smtp.gmail.com with ESMTPSA id s19-v6sm718509ejz.2.2018.11.27.11.30.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Nov 2018 11:30:47 -0800 (PST) Subject: Re: [PATCH v3 05/13] i2c: acpi: Return error pointers from i2c_acpi_new_device() To: Andy Shevchenko Cc: Darren Hart , platform-driver-x86@vger.kernel.org, "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Jonathan Cameron , Wolfram Sang , Mika Westerberg , linux-i2c@vger.kernel.org, Heikki Krogerus , linux-kernel@vger.kernel.org References: <20181127153728.47866-1-andriy.shevchenko@linux.intel.com> <20181127153728.47866-6-andriy.shevchenko@linux.intel.com> <20181127192746.GZ10650@smile.fi.intel.com> From: Hans de Goede Message-ID: <81965d66-56fb-01b1-7d5f-63afd5693778@redhat.com> Date: Tue, 27 Nov 2018 20:30:46 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20181127192746.GZ10650@smile.fi.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 27-11-18 20:27, Andy Shevchenko wrote: > On Tue, Nov 27, 2018 at 05:14:06PM +0100, Hans de Goede wrote: >> On 27-11-18 16:37, Andy Shevchenko wrote: >>> The caller would like to know the reason why the i2c_acpi_new_device() fails. >>> For example, if adapter is not available, it might be in the future and we >>> would like to re-probe the clients again. But at the same time we would like to >>> bail out if the error seems unrecoverable, such as invalid argument supplied. >>> To achieve this, return error pointer in some cases. > >>> acpi_dev_free_resource_list(&resource_list); >>> - if (ret < 0 || !info->addr) >>> - return NULL; >>> + if (!info->addr) >>> + return ERR_PTR(-EADDRNOTAVAIL); >>> adapter = i2c_acpi_find_adapter_by_handle(lookup.adapter_handle); >>> if (!adapter) >>> - return NULL; >>> + return ERR_PTR(-ENODEV); > >> Why not simply return -EPROBE_DEFER here (and simplify the callers a lot). > >> This is the only case where we really want to defer. > >>> + client = i2c_new_device(adapter, info); >>> + if (!client) >>> + return ERR_PTR(-ENODEV); >> >> If you look at i2c_new_device, it can fail because it is >> out of memory, the i2c slave address is invalid, or >> their already is an i2c slave with the same address, >> iow if this were to return an ERR_PTR itself, this >> would return -ENOMEM, -EINVAL or -EBUSY and never >> -EPROBE_DEFER. > > It would change the behaviour. Yes it would change behaviour, for the better, all the errors from i2c_new_device() (*) will not go away when we retry later, so responding with probe-deferring to them is not useful. > In any case, it's only two users and both written by you, so, just to be sure > you aware of this change and bless it. I'm aware and you've my ack for this change. Regards, Hans *) with exception of -ENOMEM which should never happen