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SubjectRe: [PATCH] of: base: Change logic in of_alias_get_alias_list()
On Mon, Oct 8, 2018 at 7:19 AM Michal Simek <michal.simek@xilinx.com> wrote:
>
> Check compatible string first before setting up bit in bitmap to also
> cover cases that allocated bitfield is not big enough.
> Show warning about it but let driver to continue to work with allocated
> bitfield to keep at least some devices (included console which
> is commonly close to serial0) to work.
>
> Fixes: b1078c355d76 ("of: base: Introduce of_alias_get_alias_list() to check alias IDs")
> Fixes: ae1cca3fa347 ("serial: uartps: Change uart ID port allocation")
> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> ---
>
> I have looked at it and I don't think there should be necessary to
> report error immediately back with partially initialized bitfield.
> The reason is that still there could be a console device which is most
> likely below that max limit and it is worth to return at least that nbits
> properly filled.
> It will also enable cases that you can still continue to use aliases
> higher then fields prepared for devices without alias.

Seems reasonable. Plus if you had a new dtb which added an alias
greater than what the OS version supports, you would break that
system.

>
> To be fixed patches are present in tty-next branch.
>
> ---
> drivers/of/base.c | 22 ++++++++++++----------
> drivers/tty/serial/xilinx_uartps.c | 2 +-
> 2 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 908de45f966b..0b9611e196d1 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -1953,13 +1953,15 @@ int of_alias_get_id(struct device_node *np, const char *stem)
> * The function travels the lookup table to record alias ids for the given
> * device match structures and alias stem.
> *
> - * Return: 0 or -ENOSYS when !CONFIG_OF
> + * Return: 0 or -ENOSYS when !CONFIG_OF or
> + * -EINVAL if alias ID is greater then allocated nbits

I think EOVERFLOW or ERANGE would be better as those are less common
and I take EINVAL as the caller made an error.

> */
> int of_alias_get_alias_list(const struct of_device_id *matches,
> const char *stem, unsigned long *bitmap,
> unsigned int nbits)
> {
> struct alias_prop *app;
> + int ret = 0;
>
> /* Zero bitmap field to make sure that all the time it is clean */
> bitmap_zero(bitmap, nbits);
> @@ -1976,21 +1978,21 @@ int of_alias_get_alias_list(const struct of_device_id *matches,
> continue;
> }
>
> - if (app->id >= nbits) {
> - pr_debug("%s: ID %d greater then bitmap field %d\n",
> - __func__, app->id, nbits);
> - continue;
> - }
> -
> if (of_match_node(matches, app->np)) {
> pr_debug("%s: Allocated ID %d\n", __func__, app->id);
> - set_bit(app->id, bitmap);
> +
> + if (app->id >= nbits) {
> + pr_warn("%s: ID %d >= than bitmap field %d\n",
> + __func__, app->id, nbits);
> + ret = -EINVAL;
> + } else {
> + set_bit(app->id, bitmap);
> + }
> }
> - /* Alias exists but is not compatible with matches */
> }
> mutex_unlock(&of_mutex);
>
> - return 0;
> + return ret;
> }
> EXPORT_SYMBOL_GPL(of_alias_get_alias_list);
>
> diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
> index d452dceb0cb3..29a18103182d 100644
> --- a/drivers/tty/serial/xilinx_uartps.c
> +++ b/drivers/tty/serial/xilinx_uartps.c
> @@ -1393,7 +1393,7 @@ static int cdns_get_id(struct platform_device *pdev)
> if (!alias_bitmap_initialized) {
> ret = of_alias_get_alias_list(cdns_uart_of_match, "serial",
> alias_bitmap, MAX_UART_INSTANCES);
> - if (ret) {
> + if (ret && ret != -EINVAL) {
> mutex_unlock(&bitmap_lock);
> return ret;
> }
> --
> 1.9.1
>

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