Re: [PATCH v2 1/3] serial: 8250: allow use of non-runtime configured uart ports

["Martin Hundebøll" <martin@geanix.com>]

On 20/10/2022 16.14, Ilpo Järvinen wrote:
> On Thu, 20 Oct 2022, Martin Hundebøll wrote:
> 
>>
>>
>> On October 20, 2022 2:34:14 PM GMT+02:00, "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com> wrote:
>>> On Tue, 18 Oct 2022, Martin Hundebøll wrote:
>>>
>>>> The logic to find unused ports when registering new 8250 uart ports
>>>> searches only up to CONFIG_SERIAL_8250_RUNTIME_UART, which forces users
>>>> of external 8250 ports to increase the number of runtime ports
>>>> artificially.
>>>>
>>>> Fix this by initializing each allocated port structure with basic
>>>> settings like line number and uart operation callbacks, and by searching
>>>> the entire array of allocated ports to find an unused one.
>>>
>>> So nr_uarts no longer means "Maximum number of UARTs supported." ?
>>> Perhaps it should be reworded too.
>>>
>>
>> It never did. Confusingly, the module parameter name (nr_uarts)
>> corresponds to CONFIG_SERIAL_8250_RUNTIME_UARTS, and controls the number
>> of built-in (non-discoverable) ports. The other config,
>> CONFIG_SERIAL_8250_NR_UARTS, controls the maximum number of ports.
>>
>> We cannot change the module parameter name, so I'm not sure if we should
>> map it to another static variable in the source?
> 
> I meant that its description should be changed to match what it really
> does.

I see. Something like this?

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index f4a08fb74c31..cdac8f11194e 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1261,7 +1261,7 @@ module_param_hw(share_irqs, uint, other, 0644);
  MODULE_PARM_DESC(share_irqs, "Share IRQs with other non-8250/16x50 devices (unsafe)");
  
  module_param(nr_uarts, uint, 0644);
-MODULE_PARM_DESC(nr_uarts, "Maximum number of UARTs supported. (1-" __MODULE_STRING(CONFIG_SERIAL_8250_NR_UARTS) ")");
+MODULE_PARM_DESC(nr_uarts, "Number of built-in (non-discoverable) UARTs to initialize. (1-" __MODULE_STRING(CONFIG_SERIAL_8250_NR_UARTS) ")");
  
  module_param(skip_txen_test, uint, 0644);
  MODULE_PARM_DESC(skip_txen_test, "Skip checking for the TXEN bug at init time");