On Mon, 28 Apr 2014 22:36:13 +0000, Hartley Sweeten <HartleyS@xxxxxxxxxxxxxxxxxxx> wrote:
> Technically, these drivers are fine as-is.
They are. The proposed change falls under minor code maintenance only.
> They are all legacy comedi drivers and use the manual attach mechanism. The
> dev->board pointer is setup by the comedi core before calling the drivers
> (*attach) so the foo = comedi_board(dev) is getting the board pointer that
> was found by the core.
> Unlike most comedi legacy drivers, these drivers then do an additional "probe"
> to try and identify the board. This could result in the dev->board_ptr getting
> changed which requires updating the local variable for the board pointer.
The point is that while updating dev->board_ptr is necessary in case of the
manual attach use case, deriving the local pointer before dev->board_ptr is
decided is not. Furthermore it might be a bit risky to already have a local
pointer to a valid, but potentially wrong comedi struct preselected by the
core, although it cannot be used safely anyway until overwritten after the
manual probe is done.
Having had a short look over the comedi code I was under the impression that
the change would make the 4 affected functions consistent to the other parts
that seemingly follow the skeleton.
static int skel_attach(struct comedi_device *dev, struct comedi_devconfig *it)
{
const struct skel_board *thisboard;
struct skel_private *devpriv;
/*
* If you can probe the device to determine what device in a series
* it is, this is the place to do it. Otherwise, dev->board_ptr
* should already be initialized.
*/
/* dev->board_ptr = skel_probe(dev, it); */
thisboard = comedi_board(dev);
> These probe functions need to be looked at to see if they are actually needed.
> For now I would prefer that the existing code stay as-is.
That added about the intention of the patch, I'm fine if You want to question
the necessity of the probes as a whole and keep the legacy code meanwhile
untouched.
Regards,
Christian
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