1 $DragonFly: doc/notes/porting_drivers.txt,v 1.4 2008/04/06 19:08:30 pavalos Exp $
3 PORTING FREEBSD DRIVERS TO DRAGONFLY
5 * Copy the driver code to the appropriate DragonFly directory. For example,
6 a disk driver /usr/src/sys/dev/blah in FreeBSD would likely be
7 /usr/src/sys/dev/disk/blah in DragonFly.
9 * Keep all the CVS ids in the files for future reference point. If the files
10 don't have it, please add it to them. You can find them out from CVSWeb
11 repository or by checking out the specific source files with the FreeBSD
13 This could be automated in the case pkgsrc's SVN client had the set of
14 patches that provide this functionality.
16 * Try to keep all the CVS ids from FreeBSD for future reference. You can
17 get them by checking out the related source files with the FreeBSD SVN
18 client or having a look at their cvsweb site. A permanent solution for
19 this issue would be to patch pkgsrc's SVN client with FreeBSD patches to
20 get the IDs properly handled automatically.
22 * Remove FBSDID declaration and '#include <sys/cdefs.h>' as well.
24 * Driver local #include's probably use a <dev/blah/blah.h> path. These
25 need to be changed to "blah.h". '.' is not included in the #include
26 path in FreeBSD builds, but it is in DragonFly builds.
28 * Other #include's may reference things in <dev/...> which in DragonFly
29 reside in <bus/...>. In particular, dev/pccard becomes bus/pccard.
30 Note that defines in FreeBSD's pccard_cis.h reside in DragonFly's
33 * The following kernel functions have been renamed in DragonFly:
35 malloc(), free() etc. -> kmalloc(), kfree() etc.
36 printf() etc. -> kprintf() etc.
37 psignal() -> ksignal()
40 * MUTEX conversion - mutexes are generally replaced by spinlocks. However,
41 DragonFly spinlocks are more restrictive than FreeBSD mutexes so a
42 direct replacement is not necessarily appropriate in all cases. A lockmgr
43 lock should be used when a direct replacement is not appropriate.
44 In particular, DragonFly does not allow recursive exclusive spinlocks
45 and does not allow multiple exclusive spinlocks to be held by any given
48 Instances of <sys/mutex.h> should be replaced with <sys/spinlock.h>.
50 When replacing mutexes with spinlocks it is a good idea to rename
51 the structural field (typically 'mtx') to something else (typically 'spin').
53 The &Giant mutex is typically converted to get_mplock() and rel_mplock().
54 However, there are places where FreeBSD unlocks giant around some code and
55 then relocks giant... those should simply be removed.
57 FreeBSD has weird callout + mutex functions. DragonFly does not integrate
58 the two. Instead, the driver in DragonFly must obtain the spinlocks
59 in question in the callback routine.
61 As a rule of thumb, MTX_DEF mutexes should be replaced with exclusive,
62 recursive lockmgr locks.
64 So, suppose the original code is using
66 you'd normally rename it to
69 and change the initialization from something like
70 mtx_init(&my_mtx, "mymtx", "whatever", MTX_DEF);
72 lockinit(&my_lock, "mylock", 0, LK_CANRECURSE);
74 Destroying it is trivial,
79 You use the same function for locking and unlocking a lockmgr lock,
83 lockmgr(&my_lock, LK_EXCLUSIVE);
87 lockmgr(&my_lock, LK_RELEASE);
89 For testing the lock status, one would use
90 lockstatus(&my_lock, curthread);
97 lockmgr(&my_lock, LK_EXCLUSIVE|LK_NOWAIT);
99 As for mtx_assert() calls, translate them like this:
101 mtx_assert(&my_mtx, MA_OWNED) -> KKASSERT(lockstatus(&my_lock, curthread) != 0)
102 mtx_assert(&my_mtx, MA_NOTOWNED) -> KKASSERT(lockstatus(&my_lock, curthread) == 0)
104 In DragonFly, lockstatus() does not return information about whether there have been
105 recursive lock acquisitions, so there is no generic way to emulate the
107 mtx_assert(&my_mtx, MA_OWNED|MA_RECURSED);
108 mtx_assert(&my_mtx, MA_OWNED|MA_NOTRECURSED);
112 * UMA conversion - generally speaking UMA should be converted to a standard
115 Note however that in FreeBSD M_NOWAIT is often used in cases where, in fact,
116 the kmalloc cannot fail without blowing something up or causing a fatal
117 (and very unexpected) I/O error. M_INTWAIT should be used for these cases.
119 * CDEVSW conversion - see other devices. Generally speaking a major number
120 is needed and a function map needs to be specified more explicitly.
122 Most calls passing struct cdev pointers are dev_t's in DragonFly.
124 All device vectors in DragonFly pass a dev_<name>_args structure pointer
125 instead of explicit arguments.
127 Strategy calls - we pass BIO's and a lot of BUF fields are in the BIO
128 in FreeBSD, but left in the BUF in DragonFly. FreeBSD for some reason
129 names its struct bio pointers 'bp', its a good idea to rename them to 'bio'
130 to avoid confusion and have a struct buf *bp = bio->bio_buf; pointer to
133 * MSLEEP/TSLEEP conversion. The DragonFly msleep/tsleep do not have 'PRI'
134 priorities. 0 should be used.
138 bus_setup_intr() - replace INTR_TYPE_* flags with 0. There is an extra
139 argument for an interrupt interlock using the sys/serializer.h interface.
140 This can either be left NULL or you can convert the spinlock(s) for
141 the driver into serializer locks and integrate the interrupt service
142 routine with a serializer.
144 * CAM CODE - cam_simq* code refcounts, so shared device queues (raid and
145 multi-channel devices) are not freed before all references have gone