From: "Theo de Raadt" <deraadt@openbsd.org>
Subject: Re: lpt should not use bufs
To: "Ted Unangst" <tedu@tedunangst.com>
Cc: tech@openbsd.org
Date: Thu, 01 May 2025 22:51:24 -0600

Wow.  Is this code originally from Xenix?

> struct buf is not meant to be a generic malloc alternative.
> 
> I think it's good, but uh, who has an lpt to test?
> 
> Index: lpt.c
> ===================================================================
> RCS file: /home/cvs/src/sys/dev/ic/lpt.c,v
> diff -u -p -r1.15 lpt.c
> --- lpt.c	15 Jan 2020 16:43:13 -0000	1.15
> +++ lpt.c	2 May 2025 04:45:12 -0000
> @@ -56,7 +56,7 @@
>  
>  #include <sys/param.h>
>  #include <sys/systm.h>
> -#include <sys/buf.h>
> +#include <sys/malloc.h>
>  #include <sys/kernel.h>
>  #include <sys/uio.h>
>  #include <sys/device.h>
> @@ -216,7 +216,7 @@ lptopen(dev_t dev, int flag, int mode, s
>  	sc->sc_control = control;
>  	bus_space_write_1(sc->sc_iot, sc->sc_ioh, lpt_control, control);
>  
> -	sc->sc_inbuf = geteblk(LPT_BSIZE);
> +	sc->sc_inbuf = malloc(LPT_BSIZE, M_DEVBUF, M_WAITOK);
>  	sc->sc_count = 0;
>  	sc->sc_state = LPT_OPEN;
>  
> @@ -280,7 +280,7 @@ lptclose(dev_t dev, int flag, int mode, 
>  	bus_space_write_1(iot, ioh, lpt_control, LPC_NINIT);
>  	sc->sc_state = 0;
>  	bus_space_write_1(iot, ioh, lpt_control, LPC_NINIT);
> -	brelse(sc->sc_inbuf);
> +	free(sc->sc_inbuf, M_DEVBUF, LPT_BSIZE);
>  
>  	LPRINTF(("%s: closed\n", sc->sc_dev.dv_xname));
>  	return 0;
> @@ -370,7 +370,8 @@ lptwrite(dev_t dev, struct uio *uio, int
>  	int error = 0;
>  
>  	while ((n = ulmin(LPT_BSIZE, uio->uio_resid)) != 0) {
> -		error = uiomove(sc->sc_cp = sc->sc_inbuf->b_data, n, uio);
> +		sc->sc_cp = sc->sc_inbuf;
> +		error = uiomove(sc->sc_cp, n, uio);
>  		if (error != 0)
>  			return error;
>  		sc->sc_count = n;
> Index: lptvar.h
> ===================================================================
> RCS file: /home/cvs/src/sys/dev/ic/lptvar.h,v
> diff -u -p -r1.4 lptvar.h
> --- lptvar.h	12 Jun 2013 19:07:40 -0000	1.4
> +++ lptvar.h	2 May 2025 04:34:40 -0000
> @@ -58,7 +58,7 @@ struct lpt_softc {
>  	struct timeout sc_wakeup_tmo;
>  
>  	size_t sc_count;
> -	struct buf *sc_inbuf;
> +	void *sc_inbuf;
>  	u_int8_t *sc_cp;
>  	int sc_spinmax;
>  	bus_space_tag_t sc_iot;	/* bus tag */
>