From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 814E8BA34; Sun, 28 Jul 2024 08:41:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722156071; cv=none; b=Ws17uljrZID3//YtBDN77lttdHP52VoETR1eljG9PA7SyZIG+LjtzCHmYfcUsJoNQk3HYdDE9GjlcDhk2BR0NfIGebm2LsXDMTbMCXjj8ONOaymhTeONBnj4BPGXOhpSCDfNZHAb6HnL7hi+0VGP9URrC502yn4TJbpoI/DWSVA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722156071; c=relaxed/simple; bh=/Bi4KvCOpUh2vfddp26zZyy0Hwn/YMVYEAibqT+vD3Q=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=oZVtN8X59YEvMB+5TmUc8xwNK9QgUdNhTiBNjiqUGL94Skg2wqGHa20yC94nIVDe1qSPvITCYifgD2/bJDHOfJhCz7EbGAfbrDClm/vGxDISclDjA06cDW36cHFerXGm87E0ne5d03QeinEOXLKyPX76xwjSnc9zEB2WkH6BX/8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=B7zYoPtv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="B7zYoPtv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 134E9C116B1; Sun, 28 Jul 2024 08:41:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722156071; bh=/Bi4KvCOpUh2vfddp26zZyy0Hwn/YMVYEAibqT+vD3Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=B7zYoPtvY9KGIMHz7fnc8lzXAp9SiHOWY1WtlwLjmV0ox4mPTc9PduF/W1ynjj5rw ZmRIyRNTqTHMhj7befls2lJ7r0WmgHi/uj9Vkq3rrxth32kTX3TinmJYwQQaTmo9xT aRbrgEp1MXDRD0pUyJHscMm4WScyiIDljTbgK0JY7pqJdigBn7vS4a4+7OD1HjLB95 yEYvzh0GP0Vgzrb7+tcUyqyWZoFBr1QuMCbTsLgF2JxIO11OpmxTX9IqgRaPqF4ufW kJW6rLo+vY2EN5dMa/r7Pawg6fh4ONp5DZOo06vcBOCNELg7Bfzu8l2Z/trH9MKtzX Ml0yFS43FKDUw== Message-ID: <27fb423a-e8f4-44c2-be1a-38d2a42a11b6@kernel.org> Date: Sun, 28 Jul 2024 10:41:05 +0200 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V5 2/2] iio: proximity: aw9610x: Add support for aw9610x proximity sensor To: Jonathan Cameron Cc: wangshuaijie@awinic.com, lars@metafoo.de, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, waqar.hameed@axis.com, linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, liweilei@awinic.com, kangjiajun@awinic.com References: <20240726061312.1371450-1-wangshuaijie@awinic.com> <20240726061312.1371450-3-wangshuaijie@awinic.com> <3ef6c902-b004-4aa0-96c9-dabd81a01a6a@kernel.org> <20240727160628.115e295e@jic23-huawei> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 27/07/2024 17:06, Jonathan Cameron wrote: > >> ... >> >>> +static int aw9610x_read_chipid(struct aw9610x *aw9610x) >>> +{ >>> + unsigned char cnt = 0; >>> + u32 reg_val; >>> + int ret; >>> + >>> + while (cnt < AW_READ_CHIPID_RETRIES) { > Why retries? >>> + ret = aw9610x_i2c_read(aw9610x, REG_CHIPID, ®_val); >>> + if (ret < 0) { >>> + cnt++; >>> + usleep_range(2000, 3000); >>> + } else { >>> + reg_val = FIELD_GET(AW9610X_CHIPID_MASK, reg_val); >>> + break; >>> + } >>> + } >>> + >>> + if (reg_val == AW9610X_CHIP_ID) >>> + return 0; >> >> So devices are detectable? Encode this in the bindings (oneOf and a >> fallback compatible) and drop unneeded entry from ID tables. > > Hi Krzysztof, > > I think this is not a good idea. > > Even though these two are detectable, this breaks if along comes a 3rd device > in the future which is truly compatible with one of these two parts but that > we don't yet know about (so can't discover). For that part we will want to > provide a meaningful fallback compatible. > > It needs to fallback to either the 3 channel or the 5 channel chip and handle > it as appropriate. (Note that this difference is non obvious as right now the > code pretends there are always 5 channels and that needs fixing). > > If the chips provided a register that told all the chip specific data like > how many channels, then sure making one fallback to the other would be fine > as future devices could use those standard registers. > > With just an Id register, we can't discover enough. Hence these two > parts should not be listed as compatible with each other. Sure Best regards, Krzysztof