1 PORTING FREEBSD DRIVERS TO DRAGONFLY
3 * Copy the driver code to the appropriate DragonFly directory. For example,
4 a disk driver /usr/src/sys/dev/blah in FreeBSD would likely be
5 /usr/src/sys/dev/disk/blah in DragonFly.
7 * Keep all the SVN IDs in the files as a future reference point. dports' SVN
8 will do that by default. When using pkgsrc's SVN client, please note the
9 files' IDs manually, either in the files themselves or in the commit message.
10 The general idea is that it must not get lost.
12 * Remove FBSDID declaration and '#include <sys/cdefs.h>' as well.
14 * Driver local #include's probably use a <dev/blah/blah.h> path. These
15 need to be changed to "blah.h". '.' is not included in the #include
16 path in FreeBSD builds, but it is in DragonFly builds.
18 * Other #include's may reference things in <dev/...> which in DragonFly
19 reside in <bus/...>. In particular, dev/pccard becomes bus/pccard.
20 Note that defines in FreeBSD's pccard_cis.h reside in DragonFly's
23 * The following kernel functions have been renamed in DragonFly:
25 malloc(), free() etc. -> kmalloc(), kfree() etc.
26 printf() etc. -> kprintf() etc.
27 psignal() -> ksignal()
30 * MUTEX conversion - mutexes are generally replaced by spinlocks. However,
31 DragonFly spinlocks are more restrictive than FreeBSD mutexes so a
32 direct replacement is not necessarily appropriate in all cases. A lockmgr
33 lock should be used when a direct replacement is not appropriate.
34 In particular, DragonFly does not allow recursive exclusive spinlocks
35 and does not allow multiple exclusive spinlocks to be held by any given
38 Instances of <sys/mutex.h> should be replaced with <sys/spinlock.h>.
40 When replacing mutexes with spinlocks it is a good idea to rename
41 the structural field (typically 'mtx') to something else (typically 'spin').
43 The &Giant mutex is typically converted to get_mplock() and rel_mplock().
44 However, there are places where FreeBSD unlocks giant around some code and
45 then relocks giant... those should simply be removed.
47 FreeBSD has weird callout + mutex functions. DragonFly does not integrate
48 the two. Instead, the driver in DragonFly must obtain the spinlocks
49 in question in the callback routine.
51 As a rule of thumb, MTX_DEF mutexes should be replaced with exclusive,
52 recursive lockmgr locks.
54 So, suppose the original code is using
56 you'd normally rename it to
59 and change the initialization from something like
60 mtx_init(&my_mtx, "mymtx", "whatever", MTX_DEF);
62 lockinit(&my_lock, "mylock", 0, LK_CANRECURSE);
64 Destroying it is trivial,
69 You use the same function for locking and unlocking a lockmgr lock,
73 lockmgr(&my_lock, LK_EXCLUSIVE);
77 lockmgr(&my_lock, LK_RELEASE);
79 For testing the lock status, one would use
80 lockstatus(&my_lock, curthread);
87 lockmgr(&my_lock, LK_EXCLUSIVE|LK_NOWAIT);
89 As for mtx_assert() calls, translate them like this:
91 mtx_assert(&my_mtx, MA_OWNED) -> KKASSERT(lockstatus(&my_lock, curthread) != 0)
92 mtx_assert(&my_mtx, MA_NOTOWNED) -> KKASSERT(lockstatus(&my_lock, curthread) == 0)
94 In DragonFly, lockstatus() does not return information about whether there have been
95 recursive lock acquisitions, so there is no generic way to emulate the
97 mtx_assert(&my_mtx, MA_OWNED|MA_RECURSED);
98 mtx_assert(&my_mtx, MA_OWNED|MA_NOTRECURSED);
102 * rwlock conversion: Use lockmgr locks
104 * UMA conversion - generally speaking UMA should be converted to a standard
107 Note however that in FreeBSD M_NOWAIT is often used in cases where, in fact,
108 the kmalloc cannot fail without blowing something up or causing a fatal
109 (and very unexpected) I/O error. M_INTWAIT should be used for these cases.
111 * CDEVSW conversion - see other devices. Generally speaking a major number
112 is needed and a function map needs to be specified more explicitly.
114 Most calls passing struct cdev pointers are dev_t's in DragonFly.
116 All device vectors in DragonFly pass a dev_<name>_args structure pointer
117 instead of explicit arguments.
119 Strategy calls - we pass BIO's and a lot of BUF fields are in the BIO
120 in FreeBSD, but left in the BUF in DragonFly. FreeBSD for some reason
121 names its struct bio pointers 'bp', its a good idea to rename them to 'bio'
122 to avoid confusion and have a struct buf *bp = bio->bio_buf; pointer to
125 * MSLEEP/TSLEEP conversion. The DragonFly msleep/tsleep do not have 'PRI'
126 priorities. 0 should be used.
130 bus_setup_intr() - replace INTR_TYPE_* flags with 0. There is an extra
131 argument for an interrupt interlock using the sys/serializer.h interface.
132 This can either be left NULL or you can convert the spinlock(s) for
133 the driver into serializer locks and integrate the interrupt service
134 routine with a serializer.
136 * CAM CODE - cam_simq* code refcounts, so shared device queues (raid and
137 multi-channel devices) are not freed before all references have gone
140 * callout_drain() should be replaced by callout_stop_sync()
142 * UNRHDR functions - DragonFly uses a more generic idr(9) subsystem
143 compatible with the Linux API of the same name
145 This LWN article describes it in details: http://lwn.net/Articles/103209/
147 A typical conversion looks like this:
151 free_unr() has to be replaced by idr_remove()
153 alloc_unr() has to be replaced by a code sequence using idr_pre_get and
154 idr_get_new such as this one:
157 if (idr_pre_get(xxx) ==0) {
158 kprintf("Memory allocation error\n");
162 ret = idr_get_new(xxx);
167 * MPASS macro - Replace it with KKASSERT
170 * PROC_LOCK / PROC_UNLOCK: to be determined on a case-by-case basis
172 Some of the time these macros can be removed entirely
174 In some cases, some locking must be done; lwkt_gettoken(&proc_token)
175 and the corresponding lwkt_reltoken() call should be good replacements
177 It is not a good idea to blindly implement these macros globally, some
178 particular proc subsystem locking semantics differ enough between FreeBSD
179 and DragonFly that this would cause problems
182 * In DragonFly 3.3 format specifier %D was removed from kprintf. As a
183 replacement functions kether_ntoa() and hexncpy() were added.
185 - Ethernet address (MAC) to its hexadecimal form:
187 char ethstr[ETHER_ADDRSTRLEN + 1];
190 kprintf("MAC address %s\n", kether_ntoa(hwaddr, ethstr)
192 - Generic conversion (block of bytes to hexadecimal form):
195 u_char mydata[6] = {1, 2, 3, 4, 5 ,6};
198 * Below statement would print:
202 kprintf("%s\n", hexncpy(mydata, 6, hexstr, HEX_NCPYLEN(6), "-"));
206 Use TAILQ_XXX_MUTABLE; the macros have the same effect, only the name is
211 Replace by lwkt_yield()
213 * vm_page_lock() and vm_page_unlock()
215 Not needed on DragonFly, remove these calls
217 * vm_pager_get_pages()
219 Removed, use vm_pager_get_page() instead