Date: Mon, 29 Jan 2001 15:46:47 +0100 From: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Peter Wemm <peter@netplex.com.au>, Brian Somers <brian@Awfulhak.org>, freebsd-arch@FreeBSD.ORG Subject: Re: Cloned open support Message-ID: <21634.980779607@critter> In-Reply-To: Your message of "Mon, 29 Jan 2001 15:39:27 %2B0100." <21576.980779167@critter>
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In message <21576.980779167@critter>, Poul-Henning Kamp writes:
>>Well, how do we support Unix98 /dev/ptmx then? This is not an academic
>>question, Linux apps are starting to do it this way and if we want to run
>>anything that uses ptys....
>>
>> int fdm fds;
>> char *slavename;
>> extern char *ptsname();
>>
>> fdm = open("/dev/ptmx", O_RDWR); /* open master */
>> grantpt(fdm); /* change permission ofslave */
>> unlockpt(fdm); /* unlock slave */
>> slavename = ptsname(fdm); /* get name of slave */
>> fds = open(slavename, O_RDWR); /* open slave */
>>
>>Opening the master allocates you a private unit of the device with its own
>>minor number.
>
>We will support it just like that. pts_clone() will recognize the "ptmx"
>name. Create a new dev_t and return it. Getting the name can be done
>with fstat(2) and devname(3). A transformation to slave name is needed
>but that will always be needed. and it will DTRT.
>
>In fact, I think you can implement this in less than 20 lines of code total.
There is one more thing you have to do: in fs/devfs/devfs_vnops.c you need
to modify the loop right before the "notfound:" label to recognize the
new entry by the dev_t instead of the name, since the clone function
creates a dev_t for another name. That will probably be faster in the
normal case as well...
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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