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Date:      Sat, 14 Oct 2006 14:12:43 +0200
From:      usleepless@gmail.com
To:        questions@freebsd.org
Subject:   Removing Giant from a driver
Message-ID:  <c39ec84c0610140512l1d8e9a6fk20dc13c8952031e@mail.gmail.com>

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Hi All,

i have been tweaking the pvr250 driver to support pvr150s/500s. now i
want to remove Giant from the code.

problem is, i am not sure what to do. i have created a mutex which
replaces the spltty and splx calls. but this crashes my box :-)

the original code looks like this:
        /*
         * Allocate a DMA tag for the scatter / gather list.
         */
        error = bus_dma_tag_create(sc->parent_dmat, 1, 0,
                                   BUS_SPACE_MAXADDR_32BIT,
                                   BUS_SPACE_MAXADDR, NULL, NULL,
                                   CXM_SG_BUFFERS
                                   * sizeof(struct cxm_sg_entry), 1,
                                   BUS_SPACE_MAXSIZE_32BIT, 0,
#if __FreeBSD_version >= 501102
                                   busdma_lock_mutex, &Giant,
#endif
                                   &sc->enc_sg.dmat);

what should it look like?

and how will i prevent the interrupt routine from interfering with
userland operations? can i place a "mtx_lock()" call in the interrupt
routine?

is there a howto somewhere?

regards,

usleep



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