linux-kernel - Re: Question about kernel interfaces

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Message-ID: <CADxyqMH4294w1Sddb8nXo6S2_JnuKkdZiM83OK8tafUJ4MbJxw@mail.gmail.com>
Date:	Sat, 7 Feb 2015 20:50:24 +0530
From:	Siddhartha De <siddhartha.de87@...il.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	"Valdis.Kletnieks@...edu" <valdis.kletnieks@...edu>
Cc:	kernelnewbies@...nelnewbies.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Question about kernel interfaces

>(For bonus points, instead of EJECT, explain how you form a curl URL
>that does TCSETS. Yes, you *do* have to handle *all* the fields of a
>struct termios, for both 32 and 64 bit environments....)


I am new to termios programming so please correct me if I am wrong ...
I did a bit of googling and well here's a probable curl url and the
corresponding pseudocode that needs to be in our interpreter


curl http://localhost:7000/IOCTL/TCSETS2?file_descriptor=fd&cflag=something&ispeed=something&ospeed=something

And here's a little pseudocode for our interpreter :-


struct termios2 tio;
// ioctl(fd, TCGETS2, &tio);

// assuming get_from_url is a function which parses the incomming url
and returns the required parameters


cflag=get_from_url (cflag ) ;
ispeed = get_from_url ( ispeed ) ;
ospeed=get_from_url(ospeed)

tio.c_cflag = cflag ;

tio.c_ispeed = ispeed;
tio.c_ospeed = ospeed;
ioctl(fd, TCSETS2, &tio);





Thanking you in anticipation ,

 Yours sincerely ,

  Kernel newbie

On Wed, Jan 21, 2015 at 11:14 PM, One Thousand Gnomes
<gnomes@...rguk.ukuu.org.uk> wrote:
> On Sun, 18 Jan 2015 15:03:55 +0530
>> Let's say you need to call an ioctl from a shell script ( I know its a
>> very rare use case but please bear with me ... :) )
>>
>> So the current way of doing it is probably to write a C program which
>> actually calls the ioctl and then call the C program from the shell
>> script ...
>
> That's how Unix is designed yes. It means that the ioctl internals are
> hidden from the scripts and the tools provided can be used instead.
>
>> and the IOCTL_EJECT ioctl would get called on /dev/cdrom
>> that is ioctl ( &handle_to_/dev/cdrom , IOCTL_EJECT , &some_buffer )
>> would get called ( by our translator running as a separate program or
>> as a service daemon )
>
> You can just run "eject". It knows about all the details of doing an
> eject.
>
> The equivalent of a "library" in shell scripts is a program. Small,
> simple tools that do one job and do it right, or at least before GNU got
> hold of them 8)
>
> Alan
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