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Wed, 11 Nov 2020 06:54:05 -0800 (PST) Sender: Guenter Roeck Subject: Re: [PATCH v2 2/4] docs: hwmon: (ltc2945): change type of val to ULL in ltc2945_val_to_reg() To: Alexandru Ardelean , linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Cc: robh+dt@kernel.org, jdelvare@suse.com, mark.thoren@analog.com, ardeleanalex@gmail.com References: <20201111091259.46773-1-alexandru.ardelean@analog.com> <20201111091259.46773-3-alexandru.ardelean@analog.com> From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= Message-ID: <41f86559-9165-40f9-e7f3-3e7f5eca7315@roeck-us.net> Date: Wed, 11 Nov 2020 06:54:03 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201111091259.46773-3-alexandru.ardelean@analog.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-hwmon@vger.kernel.org On 11/11/20 1:12 AM, Alexandru Ardelean wrote: > In order to account for any potential overflows that could occur. > > Signed-off-by: Alexandru Ardelean Thinking about it, this can only really happen if the user provides excessive values for limit attributes. Those are currently clamped later, after the conversion. I think it would be better to modify the code to apply a clamp _before_ the conversion as well instead of trying to solve the overflow problem with unsigned long long. Either case, can you send me a register dump for this chip ? I'd like to write a module test script to actually check if there are any over/underflows or other problems. Thanks, Guenter > --- > drivers/hwmon/ltc2945.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/drivers/hwmon/ltc2945.c b/drivers/hwmon/ltc2945.c > index 1cea710df668..6d4569a25471 100644 > --- a/drivers/hwmon/ltc2945.c > +++ b/drivers/hwmon/ltc2945.c > @@ -155,7 +155,7 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) > } > > static int ltc2945_val_to_reg(struct device *dev, u8 reg, > - unsigned long val) > + unsigned long long val) > { > struct ltc2945_state *st = dev_get_drvdata(dev); > struct regmap *regmap = st->regmap; > @@ -181,14 +181,14 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, > return ret; > if (control & CONTROL_MULT_SELECT) { > /* 25 mV * 25 uV = 0.625 uV resolution. */ > - val = DIV_ROUND_CLOSEST(val, 625); > + val = DIV_ROUND_CLOSEST_ULL(val, 625); > } else { > /* > * 0.5 mV * 25 uV = 0.0125 uV resolution. > * Divide first to avoid overflow; > * accept loss of accuracy. > */ > - val = DIV_ROUND_CLOSEST(val, 25) * 2; > + val = DIV_ROUND_CLOSEST_ULL(val, 25) * 2; > } > break; > case LTC2945_VIN_H: > @@ -197,7 +197,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, > case LTC2945_MAX_VIN_THRES_H: > case LTC2945_MIN_VIN_THRES_H: > /* 25 mV resolution. */ > - val /= 25; > + val = div_u64(val, 25); > break; > case LTC2945_ADIN_H: > case LTC2945_MAX_ADIN_H: > @@ -219,7 +219,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, > * dividing the reported current by the sense resistor value > * in mOhm. > */ > - val = DIV_ROUND_CLOSEST(val, 25); > + val = DIV_ROUND_CLOSEST_ULL(val, 25); > break; > default: > return -EINVAL; > @@ -247,7 +247,7 @@ static ssize_t ltc2945_value_store(struct device *dev, > struct ltc2945_state *st = dev_get_drvdata(dev); > struct regmap *regmap = st->regmap; > u8 reg = attr->index; > - unsigned long val; > + unsigned long long val; > u8 regbuf[3]; > int num_regs; > int regval; >