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[2a01:c22:6f6b:1c00:45f5:1cd8:f090:5720]) by smtp.googlemail.com with ESMTPSA id l26-20020a05600c1d1a00b003fef5e76f2csm12352454wms.0.2023.11.07.00.04.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Nov 2023 00:04:31 -0800 (PST) Message-ID: Date: Tue, 7 Nov 2023 09:04:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] i2c: i801: Use I2C_CLASS_HWMON for i2c mux children Content-Language: en-US To: Jean Delvare Cc: Andi Shyti , linux-i2c@vger.kernel.org, Peter Korsgaard , Peter Rosin References: <45c5366f-cbee-4c7d-bb62-a446935b2729@gmail.com> <20231106155036.366fb752@endymion.delvare> From: Heiner Kallweit Autocrypt: addr=hkallweit1@gmail.com; keydata= xsFNBF/0ZFUBEAC0eZyktSE7ZNO1SFXL6cQ4i4g6Ah3mOUIXSB4pCY5kQ6OLKHh0FlOD5/5/ sY7IoIouzOjyFdFPnz4Bl3927ClT567hUJJ+SNaFEiJ9vadI6vZm2gcY4ExdIevYHWe1msJF MVE4yNwdS+UsPeCF/6CQQTzHc+n7DomE7fjJD5J1hOJjqz2XWe71fTvYXzxCFLwXXbBiqDC9 dNqOe5odPsa4TsWZ09T33g5n2nzTJs4Zw8fCy8rLqix/raVsqr8fw5qM66MVtdmEljFaJ9N8 /W56qGCp+H8Igk/F7CjlbWXiOlKHA25mPTmbVp7VlFsvsmMokr/imQr+0nXtmvYVaKEUwY2g 86IU6RAOuA8E0J5bD/BeyZdMyVEtX1kT404UJZekFytJZrDZetwxM/cAH+1fMx4z751WJmxQ J7mIXSPuDfeJhRDt9sGM6aRVfXbZt+wBogxyXepmnlv9K4A13z9DVLdKLrYUiu9/5QEl6fgI kPaXlAZmJsQfoKbmPqCHVRYj1lpQtDM/2/BO6gHASflWUHzwmBVZbS/XRs64uJO8CB3+V3fa cIivllReueGCMsHh6/8wgPAyopXOWOxbLsZ291fmZqIR0L5Y6b2HvdFN1Xhc+YrQ8TKK+Z4R mJRDh0wNQ8Gm89g92/YkHji4jIWlp2fwzCcx5+lZCQ1XdqAiHQARAQABzSZIZWluZXIgS2Fs bHdlaXQgPGhrYWxsd2VpdDFAZ21haWwuY29tPsLBjgQTAQgAOBYhBGxfqY/yOyXjyjJehXLe ig9U8DoMBQJf9GRVAhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEHLeig9U8DoMSycQ AJbfg8HZEK0ljV4M8nvdaiNixWAufrcZ+SD8zhbxl8GispK4F3Yo+20Y3UoZ7FcIidJWUUJL axAOkpI/70YNhlqAPMsuudlAieeYZKjIv1WV5ucNZ3VJ7dC+dlVqQdAr1iD869FZXvy91KhJ wYulyCf+s4T9YgmLC6jLMBZghKIf1uhSd0NzjyCqYWbk2ZxByZHgunEShOhHPHswu3Am0ftt ePaYIHgZs+Vzwfjs8I7EuW/5/f5G9w1vibXxtGY/GXwgGGHRDjFM7RSprGOv4F5eMGh+NFUJ TU9N96PQYMwXVxnQfRXl8O6ffSVmFx4H9rovxWPKobLmqQL0WKLLVvA/aOHCcMKgfyKRcLah 57vGC50Ga8oT2K1g0AhKGkyJo7lGXkMu5yEs0m9O+btqAB261/E3DRxfI1P/tvDZpLJKtq35 dXsj6sjvhgX7VxXhY1wE54uqLLHY3UZQlmH3QF5t80MS7/KhxB1pO1Cpcmkt9hgyzH8+5org +9wWxGUtJWNP7CppY+qvv3SZtKJMKsxqk5coBGwNkMms56z4qfJm2PUtJQGjA65XWdzQACib 2iaDQoBqGZfXRdPT0tC1H5kUJuOX4ll1hI/HBMEFCcO8++Bl2wcrUsAxLzGvhINVJX2DAQaF aNetToazkCnzubKfBOyiTqFJ0b63c5dqziAgzsFNBF/0ZFUBEADF8UEZmKDl1w/UxvjeyAeX kghYkY3bkK6gcIYXdLRfJw12GbvMioSguvVzASVHG8h7NbNjk1yur6AONfbUpXKSNZ0skV8V fG+ppbaY+zQofsSMoj5gP0amwbwvPzVqZCYJai81VobefTX2MZM2Mg/ThBVtGyzV3NeCpnBa 8AX3s9rrX2XUoCibYotbbxx9afZYUFyflOc7kEpc9uJXIdaxS2Z6MnYLHsyVjiU6tzKCiVOU KJevqvzPXJmy0xaOVf7mhFSNQyJTrZpLa+tvB1DQRS08CqYtIMxRrVtC0t0LFeQGly6bOngr ircurWJiJKbSXVstLHgWYiq3/GmCSx/82ObeLO3PftklpRj8d+kFbrvrqBgjWtMH4WtK5uN5 1WJ71hWJfNchKRlaJ3GWy8KolCAoGsQMovn/ZEXxrGs1ndafu47yXOpuDAozoHTBGvuSXSZo ythk/0EAuz5IkwkhYBT1MGIAvNSn9ivE5aRnBazugy0rTRkVggHvt3/7flFHlGVGpBHxFUwb /a4UjJBPtIwa4tWR8B1Ma36S8Jk456k2n1id7M0LQ+eqstmp6Y+UB+pt9NX6t0Slw1NCdYTW gJezWTVKF7pmTdXszXGxlc9kTrVUz04PqPjnYbv5UWuDd2eyzGjrrFOsJEi8OK2d2j4FfF++ AzOMdW09JVqejQARAQABwsF2BBgBCAAgFiEEbF+pj/I7JePKMl6Fct6KD1TwOgwFAl/0ZFUC GwwACgkQct6KD1TwOgxUfg//eAoYc0Vm4NrxymfcY30UjHVD0LgSvU8kUmXxil3qhFPS7KA+ y7tgcKLHOkZkXMX5MLFcS9+SmrAjSBBV8omKoHNo+kfFx/dUAtz0lot8wNGmWb+NcHeKM1eb nwUMOEa1uDdfZeKef/U/2uHBceY7Gc6zPZPWgXghEyQMTH2UhLgeam8yglyO+A6RXCh+s6ak Wje7Vo1wGK4eYxp6pwMPJXLMsI0ii/2k3YPEJPv+yJf90MbYyQSbkTwZhrsokjQEaIfjrIk3 rQRjTve/J62WIO28IbY/mENuGgWehRlTAbhC4BLTZ5uYS0YMQCR7v9UGMWdNWXFyrOB6PjSu Trn9MsPoUc8qI72mVpxEXQDLlrd2ijEWm7Nrf52YMD7hL6rXXuis7R6zY8WnnBhW0uCfhajx q+KuARXC0sDLztcjaS3ayXonpoCPZep2Bd5xqE4Ln8/COCslP7E92W1uf1EcdXXIrx1acg21 H/0Z53okMykVs3a8tECPHIxnre2UxKdTbCEkjkR4V6JyplTS47oWMw3zyI7zkaadfzVFBxk2 lo/Tny+FX1Azea3Ce7oOnRUEZtWSsUidtIjmL8YUQFZYm+JUIgfRmSpMFq8JP4VH43GXpB/S OCrl+/xujzvoUBFV/cHKjEQYBxo+MaiQa1U54ykM2W4DnHb1UiEf5xDkFd4= In-Reply-To: <20231106155036.366fb752@endymion.delvare> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On 06.11.2023 15:50, Jean Delvare wrote: > Hi Heiner, > > On Tue, 31 Oct 2023 21:30:22 +0100, Heiner Kallweit wrote: >> In case there ever should be a jc42-driven device on a muxed child bus, >> we may end up with multiple logical devices, see linked discussion. >> >> jc42 is the only remaining i2c client device driver supporting >> I2C_CLASS_SPD, however it supports I2C_CLASS_HWMON too. Therefore >> we can safely switch to I2C_CLASS_HWMON on the muxed child busses. >> IMO it's more logical anyway that the muxed child busses support >> the same class that the parent supports if it's not muxed. >> >> This change is one further step towards removing I2C_CLASS_SPD. >> >> Link: https://www.spinics.net/lists/linux-i2c/msg65458.html >> Signed-off-by: Heiner Kallweit >> --- >> drivers/i2c/busses/i2c-i801.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c >> index 070999139..8c9bb2e09 100644 >> --- a/drivers/i2c/busses/i2c-i801.c >> +++ b/drivers/i2c/busses/i2c-i801.c >> @@ -1298,7 +1298,7 @@ static struct i801_mux_config i801_mux_config_asus_z8_d12 = { >> .gpio_chip = "gpio_ich", >> .values = { 0x02, 0x03 }, >> .n_values = 2, >> - .classes = { I2C_CLASS_SPD, I2C_CLASS_SPD }, >> + .classes = { I2C_CLASS_HWMON, I2C_CLASS_HWMON }, >> .gpios = { 52, 53 }, >> .n_gpios = 2, >> }; >> @@ -1307,7 +1307,7 @@ static struct i801_mux_config i801_mux_config_asus_z8_d18 = { >> .gpio_chip = "gpio_ich", >> .values = { 0x02, 0x03, 0x01 }, >> .n_values = 3, >> - .classes = { I2C_CLASS_SPD, I2C_CLASS_SPD, I2C_CLASS_SPD }, >> + .classes = { I2C_CLASS_HWMON, I2C_CLASS_HWMON, I2C_CLASS_HWMON }, >> .gpios = { 52, 53 }, >> .n_gpios = 2, >> }; >> @@ -1395,6 +1395,9 @@ static void i801_add_mux(struct i801_priv *priv) >> >> mux_config = id->driver_data; >> >> + /* Parent and mux children class support must not overlap */ >> + priv->adapter.class = 0; > > There may also be a hardware monitoring device on the parent segment on > these boards. With this change, that device will no longer be detected. > That would be a regression, so I have to nack this proposed change, > sorry. > Hmm, right. To me it seems we have a fundamental problem: The parent has no way to find out whether a detected device sits on the parent segment or whether it belongs to a muxed child segment. In the latter case the device may show up twice, as you mentioned before. And the core check "supported classes of parent and child must not overlap" doesn't consider that we may have e.g. hwmon devices on parent segment and on muxed child segment too. > The only way forward I can think of (if we want to get rid of > I2C_CLASS_SPD) would be to remove device auto-detection on children > segments completely (.class = 0 for them) and instead actively probe > for SPD EEPROMs and JC42 thermal sensors on these segments. For SPD we > should be able to just reuse i2c_register_spd(). For JC42 we would need > similar code, which doesn't exist yet. > Regarding the first part, removing auto-detection on muxed children: We have only two i2c mux drivers supporting auto-detection, i2c-mux-gpio and i2c-mux-reg. Both do not support auto-detection for DT-configured systems. Only user for i2c-mux-gpio is i801. Only user for i2c-mux-reg is drivers/platform/x86/mlx-platform, and it doesn't make use of auto-detection. So I think as first step we should remove auto-detection support from i2c-mux-reg. Then we could do the same for i2c-mux-gpio, and afterwards remove the class parameter from i2c_mux_add_adapter(). So we need an "i2c_register_jc42()" only for use by i801. What's good, because we can make this function private to i801 and won't attract any potential additional users. + i2c-mux-gpio and i2c-mux-reg maintainers