On Fri, Apr 23, 2021 at 11:03:22AM +0100, Joe Burmeister wrote: > On 23/04/2021 00:49, Florian Fainelli wrote: > > Right, which means that we should probably seek a solution within the > > SPI core itself, even if you can only test with spi-bcm2835.c chances > > are that the fix would be applicable for other controllers if done in > > the core. > I'm not sure it's possible to do in the core alone. The numb of the > issue is the core changes ctlr->num_chipselect to what is in the device > tree and some drivers are cool with that overs quietly stomp memory. 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've got a simple little patch to warn when the core expands > ctlr->num_chipselect. This warning won't go off in bcm2835 with my patch > because I am also extending ctlr->num_chipselect to the amount in the > device tree before the core does that expansion. Hopefully that new > warning would make people investigate and fix problem drivers. > >> There is protection in spi_add_device, which will catch extra added > >> later, but not ones in the device tree when the spi controller was > >> registered. > > 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?
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