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[82.46.60.197]) by smtp.gmail.com with ESMTPSA id 33sm14994985edt.57.2017.11.27.04.14.00 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 Nov 2017 04:14:01 -0800 (PST) To: Udit Kumar , Ard Biesheuvel Cc: Leif Lindholm , "edk2-devel@lists.01.org" , Varun Sethi , Graeme Gregory References: <2166aaa7-2f96-50d4-4502-bbb9b8b9ef22@linaro.org> From: Daniel Thompson Message-ID: Date: Mon, 27 Nov 2017 12:13:59 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Subject: Re: [RFC] ACPI table HID/CID allocation X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Nov 2017 12:09:42 -0000 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit On 25/11/17 12:56, Udit Kumar wrote:>> -----Original Message----- >> From: Daniel Thompson [mailto:daniel.thompson@linaro.org] >> Sent: Thursday, November 23, 2017 1:42 AM >> To: Ard Biesheuvel >> Cc: Udit Kumar ; Leif Lindholm >> ; edk2-devel@lists.01.org; Varun Sethi >> ; Graeme Gregory >> Subject: Re: [RFC] ACPI table HID/CID allocation >> > >>> >>> PRP0001 + compatible was invented to avoid the need to allocate a _HID >>> for each and every component in existence that can already be >>> identified by a DT compatible string (and little else except, e.g., a >>> I2C slave address) and is not deeply engrained in the SoC in terms of >>> clock tree, power states etc. So while internal/external may not be >>> the most accurate distinction, it is still a useful one IMHO. >> >> Hmnnn.... it sounds like jedec,spi-nor meets this test. >> >> There is only one property in the DT bindings that describes the device >> itself (fast read support) rather than its "bus address" (chip select, >> frequency). Further, that single property is obsolete, at least for >> Linux; the kernel driver now contains a quirks tables to look up by >> device ID whether fast read is supported and will use that on non-DT >> systems (and also to censor broken DT systems ;-) ). > > You mean, this more on bus frame work, how to probe slave. > Example rtc-ds3232.c , when is spi mode just need name > but for i2c mode it needs of_match_table I mean nothing more or less than that PRP0001 + compatible:jedec,spi-nor is tolerable within the ACPI tables (rather than allocating a HID) because it has no properties[1] beyond the bus configuration that ACPI can already describe I'm afraid I don't understand how rtc-ds3232.c fits into this topic; there are no documented device tree bindings for the SPI variant of this part and, in any case, an RTC should use the ACPI interfaces (rtc-cmos.c) so the choice HID is a moot point; it should not be in the ACPI tables at all. Daniel. [1] Assuming one accepts the argument that the m25p,fast-read property can be ignored. ignored.