At Fri, 5 Aug 2011 10:24:43 +0800, Scott Jiang wrote:
2011/8/4 Mark Brown broonie@opensource.wolfsonmicro.com:
On Thu, Aug 04, 2011 at 06:24:04PM +0800, Scott Jiang wrote:
My version is linux 3.0, I found snd_soc_spi_read/write didn't work at 16-8 bit mode. The addr is 16bit, the function compares reg with reg_cache_size. This certainly causes failure. In the former version, reg &= 0xff seems right. So how to use snd_soc_16_8_write now?
reg &= 0xff is clearly broken for 16 bit register values...
hw_write use 16bit reg, cache use 8bit reg, in former version
data[0] = (reg >> 8) & 0xff; data[1] = reg & 0xff; data[2] = value; reg &= 0xff; if (reg < codec->reg_cache_size) cache[reg] = value; ret = codec->hw_write(codec->control_data, data, 3);now in do_hw_write if (!snd_soc_codec_volatile_register(codec, reg) && reg < codec->driver->reg_cache_size && !codec->cache_bypass) { ret = snd_soc_cache_write(codec, reg, value); if (ret < 0) return -1; } reg > reg_cache_size, so will not write to cache
The problem is that the current cache code doesn't take care of special register-index values like 16_8 case. In 16-8 case, usually only the lower 8 bit indicates the real register index while the upper 8 bit is some (usually constant) control bits. Thus, it worked well in the former version by masking with 0xff.
A quick fix would to introduce again the 0xff masking. Of course, this isn't a right thing, but would be enough for the current code, as regmap will replace in future anyway.
Note that all this code will be replaced with regmap for 3.2.
Do you mean I must update to 3.2 to solve this problem?
Not yet :) regmap has the same issue for now, as far as I see.
I guess reg_mask_bits is needed in struct regmap_config in addition for supporting such a case.
thanks,
Takashi