RE: [PATCH 1/2] drivers:staging:ti-st: move TI_ST from staging

Savoy, Pavan
2010-10-07T14:52:52Z

> -----Original Message-----
> From: Jiri Slaby [mailto:jirislaby@gmail.com]
> Sent: Thursday, October 07, 2010 2:59 AM
> To: Savoy, Pavan
> Cc: gregkh@suse.de; linux-kernel@vger.kernel.org; devel@driverdev.osuosl.org;
> alan@lxorguk.ukuu.org.uk
> Subject: Re: [PATCH 1/2] drivers:staging:ti-st: move TI_ST from staging
>
> On 10/07/2010 12:36 AM, Savoy, Pavan wrote:
> >>>>> +int st_core_init(struct st_data_s **core_data)
> >>>>> +{
> >>>>> + struct st_data_s *st_gdata;
> >>>>> + long err;
> >>>>> + static struct tty_ldisc_ops *st_ldisc_ops;
> >>>>> +
> >>>>> + /* populate and register to TTY line discipline */
> >>>>> + st_ldisc_ops = kzalloc(sizeof(*st_ldisc_ops), GFP_KERNEL);
> >>>>> + if (!st_ldisc_ops) {
> >>>>> + pr_err("no mem to allocate");
> >>>>> + return -ENOMEM;
> >>>>> + }
> >>>> This can be static structure, you don't need to allocate this on heap.
> >>>> It should be a singleton.
> >>>
> >>> Yes, I got this comment before, but is it just a style issue?
> >>> I want to keep this in heap because some day, I hope TTY ldics have their
> >> own
> >>> private_data, which I can pass around like the tty_struct's data.
> >>> and having them in heap, I plan to keep a reference to ops structure, so
> >> that I
> >>> can pass around and use ops->private_data everywhere ..
> >>
> >> I doubt ldisc ops will ever have ->private_data. What would you need it
> >> for? The ops generally work with ttys which have ->disc_data.
> >
> > Yes, But in this case, I required something which can be set during
> ldisc_register, and can be picked up during tty_open.
>
> Why? ldiscs are per-system, singletons, not per-device. So you should
> not bind to them any device specific info.

Per-system? I don't understand this.
There can be ldisc for each individual TTY, so doesn't that make it per device?
Or to be even more specific, it makes it per-TTY which is mapped to a particular device, UART/a-set of usb-endpoints etc...

This driver in fact does just that, it is a driver which allows sharing of the TTY by many other drivers (I call it the protocol drivers).

> --
> js