Date: Fri, 15 Sep 2006 17:10:16 +0200 From: Hans Petter Selasky <hselasky@c2i.net> To: John Baldwin <jhb@freebsd.org> Cc: Perforce Change Reviews <perforce@freebsd.org> Subject: Re: PERFORCE change 106148 for review Message-ID: <200609151710.17572.hselasky@c2i.net> In-Reply-To: <200609151039.16523.jhb@freebsd.org> References: <200609151417.k8FEHSFx098273@repoman.freebsd.org> <200609151039.16523.jhb@freebsd.org>
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On Friday 15 September 2006 16:39, you wrote: > On Friday 15 September 2006 10:17, Hans Petter Selasky wrote: > > http://perforce.freebsd.org/chv.cgi?CH=106148 > > > > Change 106148 by hselasky@hselasky_mini_itx on 2006/09/15 14:17:12 > > > > Initialize all driver_t structures by record. Bugfix: Some of the > > modem drivers did not use the "ucom_devclass". Make sure that all > > modem drivers use this devclass. > > That doesn't actually matter. Also, no other drivers use this style to > initialize their driver_t. If you really wanted to do a change, you should > change them to use DEFINE_CLASS macros to define a KOBJ class instead. Ok. Will consider that next time. > BTW, why the devclass doesn't matter: the devclass_t is just a pointer to > a device class. The device classes are based on the driver name, so if you > add a new driver with the name "foo", it will look up the device class by > name ("foo"), creating one if it doesn't exist. My implementation for NetBSD works like this: static u_int8_t devclass_create(devclass_t *dc_pp) { if (dc_pp == NULL) { return 1; } if (dc_pp[0] == NULL) { dc_pp[0] = malloc(sizeof(**(dc_pp)), M_DEVBUF, M_WAITOK|M_ZERO); if (dc_pp[0] == NULL) { return 1; } } return 0; } static const struct bsd_module_data * devclass_find_create(const char *classname) { const struct bsd_module_data *mod; for(mod = &bsd_module_data_start[0]; mod < &bsd_module_data_end[0]; mod++) { if(mod->mod_name && (strcmp(classname, mod->mod_name) == 0)) { if(devclass_create(mod->devclass_pp)) { continue; } return mod; } } return NULL; } > It then saves a pointer to > that device class object in the devclass_t pointer specified in > DRIVER_MODULE(). So, by making them all share the same devclass_t, they are > all just going to overwrite the same pointer when the driver module loads. No, wrong. The devclass_t pointer is not overwritten if it is already initialized! > To be honest, most drivers don't even use the devclass pointer, and I'd > actually like to axe it and make the few drivers that do care use > 'devclass_find("foo")' when they need the devclass pointer instead. I need the devclass to get unique unit numbers. --HPS
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