On Thu, Apr 11, 2019 at 5:12 PM Brandon Maier
<brandon.maier@xxxxxxxxxxxxxxxxxxx> wrote:
Hi Brandon,
Thanks! This is useful.
>
> The fpga-mgr assigns device IDs based on the order each driver calls
> fpga_mgr_register(). This is fine for systems with one FPGA, but if
> multiple FPGAs are in use, the device ID can change as probe order
> changes across reboots or configuration changes.
>
> This makes it difficult to use the sysfs attributes, as the device path
> may change. Instead allow a static ID to be set by adding fpgaX props
> to the devicetree /aliases. Falling back to incrementing IDs if none are
> provided.
>
> This is based on the function rtc_device_get_id() in drivers/rtc/class.c
> (9d2b7e532da8 rtc: honor device tree /alias entries when assigning IDs).
>
> Signed-off-by: Brandon Maier <brandon.maier@xxxxxxxxxxxxxxxxxxx>
Acked-by: Alan Tull <atull@xxxxxxxxxx>
Alan
> ---
> drivers/fpga/fpga-mgr.c | 22 +++++++++++++++++++++-
> 1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
> index c3866816456a..d8b7e7a61117 100644
> --- a/drivers/fpga/fpga-mgr.c
> +++ b/drivers/fpga/fpga-mgr.c
> @@ -551,6 +551,26 @@ void fpga_mgr_unlock(struct fpga_manager *mgr)
> }
> EXPORT_SYMBOL_GPL(fpga_mgr_unlock);
>
> +static int fpga_mgr_get_id(struct device *dev)
> +{
> + int of_id = -1, id = -1;
> +
> + if (dev->of_node)
> + of_id = of_alias_get_id(dev->of_node, "fpga");
> +
> + if (of_id >= 0) {
> + id = ida_simple_get(&fpga_mgr_ida, of_id, of_id + 1,
> + GFP_KERNEL);
> + if (id < 0)
> + dev_warn(dev, "/aliases ID %d not available\n", of_id);
> + }
> +
> + if (id < 0)
> + id = ida_simple_get(&fpga_mgr_ida, 0, 0, GFP_KERNEL);
> +
> + return id;
> +}
> +
> /**
> * fpga_mgr_create - create and initialize a FPGA manager struct
> * @dev: fpga manager device from pdev
> @@ -586,7 +606,7 @@ struct fpga_manager *fpga_mgr_create(struct device *dev, const char *name,
> if (!mgr)
> return NULL;
>
> - id = ida_simple_get(&fpga_mgr_ida, 0, 0, GFP_KERNEL);
> + id = fpga_mgr_get_id(dev);
> if (id < 0) {
> ret = id;
> goto error_kfree;
> --
> 2.20.1
>
