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Date: Sat, 29 Mar 2014 11:53:13 +0100 From: Lars-Peter Clausen <lars@...afoo.de> To: Songhee Baek <sbaek@...dia.com> CC: Arun Shamanna Lakshmi <aruns@...dia.com>, "'lgirdwood@...il.com'" <lgirdwood@...il.com>, "'broonie@...nel.org'" <broonie@...nel.org>, "'swarren@...dotorg.org'" <swarren@...dotorg.org>, "'alsa-devel@...a-project.org'" <alsa-devel@...a-project.org>, "'tiwai@...e.de'" <tiwai@...e.de>, "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org> Subject: Re: [alsa-devel] [PATCH] ASoC: Add support for multi register mux On 03/29/2014 03:30 AM, Songhee Baek wrote: >> -----Original Message----- >> From: Songhee Baek >> Sent: Friday, March 28, 2014 11:10 AM >> To: 'Lars-Peter Clausen' >> Cc: Arun Shamanna Lakshmi; 'lgirdwood@...il.com'; 'broonie@...nel.org'; >> 'swarren@...dotorg.org'; 'alsa-devel@...a-project.org'; 'tiwai@...e.de'; >> 'linux-kernel@...r.kernel.org' >> Subject: RE: [alsa-devel] [PATCH] ASoC: Add support for multi register mux >> >> >>>> On 03/26/2014 11:41 PM, Songhee Baek wrote: >>>>>> On 03/26/2014 01:02 AM, Arun Shamanna Lakshmi wrote: >>>>>> >>>>>> The way you describe this it seems to me that a value array for >>>>>> this kind of mux would look like. >>>>>> >>>>>> 0x00000000, 0x00000000, 0x00000001 0x00000000, 0x00000000, >>>>>> 0x00000002 0x00000000, 0x00000000, 0x00000003 0x00000000, >>>>>> 0x00000000, 0x00000004 0x00000000, 0x00000000, 0x00000008 ... >>>>>> >>>>>> That seems to be extremely tedious. If the MUX uses a one hot >>>>>> encoding how about storing the index of the bit in the values >>>>>> array and use (1 << value) when writing the value to the register? >>>>> >>>>> If we store the index of the bit, the value will be duplicated for >>>>> each >>>> registers inputs since register has 0 to 31bits to shift, then we >>>> need to decode the index to interpret value for which registers to >>>> set. If we need to interpret the decoded value of index, it is >>>> better to have custom put/get function in our driver, isn't it? >>>>> >>>> >>>> I'm not sure I understand. If you use (val / 32) to pick the >>>> register and (val % >>>> 32) to pick the bit in the register this should work just fine. >>>> Maybe I'm missing something. Do you have a real world code example >>>> of of the this type of enum is used? >>>> >>> >>> I can use val/32 and val%32 for this multi register mux. >> > With this logic, put function would be easy however get function becomes tedious due to looping on each bit per register for 3 of them in our case. Rather, it would be easy to identify a unique MUX_OFFSET to distinguish between the 3 > registers as shown in the code below. I'm not sure I understand how that MUX_OFFSET would work. To get the selected mux output you can use the ffs instruction. foreach(reg) { reg_val = read(reg) & mask; if (reg_val != 0) { val = __ffs(reg_val); break; } } - Lars -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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