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([2405:201:d02f:d899:2028:7962:400:43b6]) by smtp.gmail.com with ESMTPSA id u20-20020aa78394000000b00608dae58695sm19080379pfm.209.2023.03.27.08.47.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Mar 2023 08:47:20 -0700 (PDT) Message-ID: <2077c7e1-cf69-8648-20ac-23793f92ad14@9elements.com> Date: Mon, 27 Mar 2023 21:17:16 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v2 2/2] leds: max597x: Add support for max597x To: Christophe JAILLET , Lee Jones , Pavel Machek Cc: Patrick Rudolph , linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org References: <20230323194550.1914725-1-Naresh.Solanki@9elements.com> <20230323194550.1914725-2-Naresh.Solanki@9elements.com> <688423c6-ba98-002c-efe5-7b0997d6af73@9elements.com> Content-Language: en-US From: Naresh Solanki In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org Hi, On 24-03-2023 09:06 pm, Christophe JAILLET wrote: > Le 24/03/2023 à 11:54, Naresh Solanki a écrit : >> Hi, >> >> On 24-03-2023 01:48 am, Christophe JAILLET wrote: >>> Le 23/03/2023 à 20:45, Naresh Solanki a écrit : >>>> From: Patrick Rudolph >>>> >>>> max597x is hot swap controller with indicator LED support. >>>> This driver uses DT property to configure led during boot time & >>>> also provide the LED control in sysfs. >>>> > > [...] > > >>>> +static int max597x_led_probe(struct platform_device *pdev) >>>> +{ >>>> +    struct device_node *np = dev_of_node(pdev->dev.parent); >>>> +    struct regmap *regmap = dev_get_regmap(pdev->dev.parent, NULL); >>>> +    struct device_node *led_node; >>>> +    struct device_node *child; >>>> +    int ret = 0; >>>> + >>>> +    if (!regmap) >>>> +        return -EPROBE_DEFER; >>>> + >>>> +    led_node = of_get_child_by_name(np, "leds"); >>>> +    if (!led_node) >>>> +        return -ENODEV; >>>> + >>>> +    for_each_available_child_of_node(led_node, child) { >>>> +        u32 reg; >>>> + >>>> +        if (of_property_read_u32(child, "reg", ®)) >>>> +            continue; >>>> + >>>> +        if (reg >= MAX597X_NUM_LEDS) { >>>> +            dev_err(&pdev->dev, "invalid LED (%u >= %d)\n", reg, >>>> +                MAX597X_NUM_LEDS); >>>> +            continue; >>>> +        } >>>> + >>>> +        ret = max597x_setup_led(&pdev->dev, regmap, child, reg); >>>> +        if (ret < 0) >>>> +            of_node_put(child); >>> >>> This of_node_put() looks odd to me. >> Not sure if I get this right but if led setup fails of_node_put should >> be called. > > My understanding is that this of_node_put() is there in case of error, > to release what would otherwise never be released by > for_each_available_child_of_node() if we exit early from the loop. > > If the purpose is to release a reference taken in max597x_setup_led() in > case of error: >    - this should be done IMHO within max597x_setup_led() directly >    - there should be a of_node_get() somewhere in max597x_setup_led() >      (after: >     if (of_property_read_string(nc, "label", &led->led.name)) >         led->led.name = nc->name; >       + error handling path,  *or* >      just before the final return ret; when we know that everything is > fine, >      if I understand correctly the code) > > Is the reference taken elsewhere? > Did I miss something obvious? > > One of the reference is "drivers/leds/leds-sc27xx-bltc.c" line 311 Please do let me know if I have to do anything about it. >>> "return ret;" or "break;" missing ? >>> >> Didn't add a break so that it can continue initializing remaining led >> if any. > > Ok. Don't know the code enough to see if correct or not, but based on my > comment above, I think that something is missing in max597x_setup_led() > and that errors should be silently ignored here. In my implementation, I have chosen to continue with the next LED if an error occurs, rather than aborting the 'for loop' with an error. I have seen other implementations also done in a similar way. Do you have any further inputs or suggestions on this approach. > > CJ > >>>> +    } >>>> + >>>> +    return ret; >>>> +} >>>> + > > [...] > Regards, Naresh