Roughly how much kernel memory is allocated for a UART by
uart_register_driver() for UARTS that never get instantiated by
uart_add_one_port()?
A few KB, tens of KB, hundreds of KB?
Many of the serial-core drivers have a configurable "number of uarts"
value that goes into a 'uart_driver' struct:
static struct uart_driver foo_uart_driver =
{
.owner = THIS_MODULE,
.driver_name = DRV_NAME,
.dev_name = "ttyFoo",
.nr = CONFIG_SERIAL_FOO_NR_UARTS,
};
which is then passed to uart_register_driver:
rc = uart_register_driver(&foo_uart_driver);
which then allocates stuff as approprite depending on the .nr value.
I'm reading through the tty and serial-core code trying to figure out
how much memory is allocated per uart by that call, but I'm not at all
confident I've found all (or even most) of it.
I'm considering setting .nr to 256 in order to handle large
configurations without burdening the user with building the drivier,
installing it, loading it, searching through the syslog for the
failures messages, troubleshooting the failure, changing
CONFIG_SERIAL_FOO_NR_UARTS, and repeating.
But if that's going to allocate huge amounts of kernel memory that
don't get used in the common case where there are only 4 or 8 UARTs it
may be a bad idea...
--
Grant Edwards grant.b.edwards Yow! I am NOT a nut....
at
gmail.com
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