On Fri, Apr 23, 2021 at 03:12:11PM +0100, Joe Burmeister wrote: > On 23/04/2021 12:57, Mark Brown wrote: > > I wouldn't expect any controller to be OK with that? Drivers can store > > per-client data in spi_device->controller_data which doesn't need > > scaling (but is also not so helpful if you need to look at clients other > > than the one you're currently controlling). > I can see a number which certainly wouldn't. Though I don't want to > assume that all don't. Yeah, some won't - some do also rely on system specific assumptions about what's possible but there's not really mechanisms for declaring that. > If we are happy just not letting the core expand num_chipselect that > does stop the condition on everything. > Any controller that can go higher without issue could them have their > num_chipselect set to what their real limit is if this enforcement > causes an issue. Part of the issue here is that there has been some variation in how num_chipselect is interpreted with regard to GPIO based chip selects over time. It *should* be redundant, I'm not clear why it's in the generic bindings at all but that's lost to history AFAICT. > >>> Not sure I follow you, if we have the overlay before > >>> spi_register_controller() is called, how can the check there not > >>> trigger? And if we load the overlay later when the SPI controller is > >>> already registered, why does not spi_add_device()'s check work? > >> I think it might be a RPI thing. I think it is merging in the overlay > >> and giving Linux one already merged. > > If the overlay is handled by the bootloader then from the point of view > > of Linux there is no overlay - sounds like there's an issue in the > > overlay, it should be overriding something that it doesn't? > Does it matter if the final device tree was compiled like that in the > first place or merge into that by the bootloader? It matters in the context of a discussion of ordering between loading the overlay and spi_register_controller() - it's clearly not loaded afterwards. > Of course we could just raise BCM2835_SPI_NUM_CS to 8 or more if that is > preferred. Does seams like the dynamic solution is less favoured. The best thing would be to have it not have a single array of chip select specific data and instead store everything in the controller_data that's there per-device.
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