From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <50081AC0.10703@metafoo.de> Date: Thu, 19 Jul 2012 16:33:36 +0200 From: Lars-Peter Clausen MIME-Version: 1.0 To: Marek Vasut CC: linux-iio@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jonathan Cameron , Wolfgang Denk , Juergen Beisert Subject: Re: [PATCH] IIO: Add basic MXS LRADC driver References: <1341368129-20468-1-git-send-email-marex@denx.de> <201207050148.27289.marex@denx.de> <4FF55149.2080801@metafoo.de> <201207191623.14492.marex@denx.de> In-Reply-To: <201207191623.14492.marex@denx.de> Content-Type: text/plain; charset=ISO-8859-1 List-ID: On 07/19/2012 04:23 PM, Marek Vasut wrote: > Dear Lars-Peter Clausen, > > Sorry for my late reply, got busy with other crazy stuff. > > [...] > >>>> Is there any reason not to use the mxs_lradc struct directly has the iio >>>> data? >>> >>> I explained it below in the patch. I hope we'll eventually support the >>> delay triggers, which will need 4 separate IIO devices. And this is >>> where this structure will be augmented by other components. >> >> Ok I saw the comment, but it wasn't obvious to me that delay channels will >> require multiple IIO devices. Might make sense to state this explicitly. > > Fixed. > >>>>> [...] >>>>> >>>>> + >>>>> +/* >>>>> + * Channel management >>>>> + * >>>>> + * This involves crazy mapping between 8 virtual channels the CTRL4 >>>>> register + * can harbor and 16 channels total this hardware supports. >>>>> + */ >>>> >>>> I suppose this means only a maximum 8 channels can be active at a time. >>>> I've recently posted a patch which makes it easy to implement such a >>>> restriction. http://www.spinics.net/lists/linux-iio/msg05936.html and >>>> http://www.spinics.net/lists/linux-iio/msg05935.html for an example >>>> validate callback implementation. In your case you'd check for >>>> bitmap_weight(...) <= 8. Those patches are not yet in IIO though. >>> >>> This is good. When do you expect this to hit linux-next possibly? Or at >>> least linux-iio? >> >> soon, hopefully. > > So I checked this, not sure how it'll help me though. Right now with your driver you can enable any combination of channels. If more than 8 channels are enabled and you start sampling it will fail, since not all channels can be mapped. With those patch you can implement a validate callback and check for bitmap_weight(scan_mask) <= 8. This will ensure that it is not possible to select more than 8 channels at once, which again means that starting sampling can't fail of this. - Lars