On Tue, Jul 18, 2017 at 04:17:41PM +0800, AceLan Kao wrote:
> Hi all,
>
> I'm working on a backlight driver which read/write commands through
> standard UART port, but got some issues.
>
> 1. The UART port defined in BIOS/DSDT as HID="DELL0501" and
> CID="PNP0501" and uses address 0x3F8 and IRQ 4, so the port will be
> created by 8250_pnp driver as ttyS0.
>
> Name (_HID, "DELL0501") // _HID: Hardware ID
> Name (_CID, EisaId ("PNP0501") /* 16550A-compatible
> COM Serial Port */) // _CID: Compatible ID
> Name (_DDN, "COM5") // _DDN: DOS Device Name
>
> 2. I can send/receive commands from userspace app by opening
> /dev/ttyS0 to change the backlight brightness. This makes sure the
> UART channel works.
>
> 3. What I want is to implement a driver which create a backlight
> interface, so userspace GUI can access it without changing any code.
> The driver is as attached.
>
> 4. The issue is that, I have to open and close the "/dev/ttyS0" before
> inserting my driver. It can be done by userspace app(on some system,
> systemd check/open every serial ports automatically after booting up)
> or done in the driver by filp_open(). If the port(ttyS0) doesn't be
> opened before inserting my driver, I can't read any data from UART.
> And after inserting my driver, the ttyS0 won't respond any commands I
> sent from userspace app.
>
> I have no idea why it doesn't work, and I'm not pretty sure if I did
> it correct. Please help me to check it.
> Thanks.
Why not use the serdev interface, or see how the speakup subsystem
handles talking to serial ports. That might help you out here.
thanks,
greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
