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bh=eaWT11VKWyn2uORRCibZSFi/qJOW4Eg9p6rFjiWryHA=; b=QcpgSA3Rhas23tKi9RnCpe8LXzgiIfV8VgQpaKCx6Tn8XD+jhNfzH5/DFtWP107IjK GAHrPK3fvOyCobRAhFVMzCfWEdcyf/2HhHDKR5kfvYck3MrHwcWK/J3yJJKseEAAHucz DdqegrYNHX7jUpNGgxJ03D7Wg7BLxTX5Fba6e7HSPRxZ6gjxtUT5dePVXyNt+8kynS6Q /GnToT6ectVNIrPJ1HbgBoX3LNaC+IpaM0VGbr6Zr1LPjEH8qmC1dwqWPk4+yBqJ20JY g1EIWma5eFStcalsb+xqrprAMi3TbcPcAby0jALMU/ZFRwe2DmpFMwIo58ZWPAX+ZWzy uuzQ== X-Gm-Message-State: AOAM5311wV2IF91y+3SHj854a6K/pjuX1jbBJiavL7j0fsiTRb6jmZNO oFQY0C5Fn0097SjeALztDTiK2is667rv+GXYqYQ= X-Google-Smtp-Source: ABdhPJzkfNqlGQjHMubNaQg1+u/L5l/ZyU+t/fc5z3CN7u2JModVJN9BwjfvAFAl7He5OG+eH6pj0JqzvTmmOmAVqbk= X-Received: by 2002:a05:6e02:1be1:: with SMTP id y1mr5487782ilv.101.1613049275631; Thu, 11 Feb 2021 05:14:35 -0800 (PST) MIME-Version: 1.0 References: <20210211123353.78963-1-alexandru.ardelean@analog.com> <20210211123353.78963-4-alexandru.ardelean@analog.com> In-Reply-To: <20210211123353.78963-4-alexandru.ardelean@analog.com> From: Alexandru Ardelean Date: Thu, 11 Feb 2021 15:14:23 +0200 Message-ID: Subject: Re: [PATCH 3/3] tools: iio: add example for high-speed buffer support To: Alexandru Ardelean Cc: LKML , linux-iio , Lars-Peter Clausen , "Hennerich, Michael" , Jonathan Cameron , =?UTF-8?B?TnVubyBTw6E=?= , "Bogdan, Dragos" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Thu, Feb 11, 2021 at 2:38 PM Alexandru Ardelean wrote: > > Following a recent update to the IIO buffer infrastructure, this change > adds a basic example on how to access an IIO buffer via the new mmap() > interface. > > The ioctl() for the high-speed mode needs to be enabled right from the > start, before setting any parameters via sysfs (length, enable, etc), to > make sure that the mmap mode is used and not the fileio mode. > > Signed-off-by: Alexandru Ardelean > --- > tools/iio/iio_generic_buffer.c | 184 +++++++++++++++++++++++++++++++-- > 1 file changed, 178 insertions(+), 6 deletions(-) > > diff --git a/tools/iio/iio_generic_buffer.c b/tools/iio/iio_generic_buffer.c > index fdd08514d556..af1a944edcdb 100644 > --- a/tools/iio/iio_generic_buffer.c > +++ b/tools/iio/iio_generic_buffer.c > @@ -31,6 +31,7 @@ > #include > #include > #include > +#include > #include > #include "iio_utils.h" > > @@ -239,6 +240,133 @@ static int enable_disable_all_channels(char *dev_dir_name, int buffer_idx, int e > return 0; > } > > +struct mmap_block { > + struct iio_buffer_block block; > + void *addr; > +}; > + > +static struct mmap_block *enable_high_speed(int buf_fd, unsigned int block_size, > + int nblocks) > +{ > + struct iio_buffer_block_alloc_req req = { 0 }; > + struct mmap_block *mmaps = NULL; > + int mmaps_cnt = 0; > + int i, ret; > + > + /** > + * Validate we can do high-speed by issuing BLOCK_FREE ioctl. > + * If using just BLOCK_ALLOC it's distinguish between ENOSYS > + * and other error types. > + */ > + ret = ioctl(buf_fd, IIO_BUFFER_BLOCK_FREE_IOCTL, 0); > + if (ret < 0) { > + errno = ENOSYS; > + return NULL; > + } > + > + /* for now, this */ > + req.id = 0; > + req.type = 0; > + req.size = block_size; > + req.count = nblocks; > + > + ret = ioctl(buf_fd, IIO_BUFFER_BLOCK_ALLOC_IOCTL, &req); > + if (ret < 0) > + return NULL; > + > + if (req.count == 0) { > + errno = ENOMEM; > + return NULL; > + } > + > + if (req.count < nblocks) { > + fprintf(stderr, "Requested %d blocks, got %d\n", > + nblocks, req.count); > + errno = ENOMEM; > + return NULL; > + } > + > + mmaps = calloc(req.count, sizeof(*mmaps)); > + if (!mmaps) { > + errno = ENOMEM; > + return NULL; > + } > + > + for (i = 0; i < req.count; i++) { > + mmaps[i].block.id = i; > + ret = ioctl(buf_fd, IIO_BUFFER_BLOCK_QUERY_IOCTL, &mmaps[i].block); > + if (ret < 0) > + goto error; > + > + ret = ioctl(buf_fd, IIO_BUFFER_BLOCK_ENQUEUE_IOCTL, &mmaps[i].block); > + if (ret < 0) > + goto error; > + > + mmaps[i].addr = mmap(0, mmaps[i].block.size, > + PROT_READ | PROT_WRITE, MAP_SHARED, > + buf_fd, mmaps[i].block.data.offset); > + > + if (mmaps[i].addr == MAP_FAILED) > + goto error; > + > + mmaps_cnt++; > + } > + > + return mmaps; > + > +error: > + for (i = 0; i < mmaps_cnt; i++) > + munmap(mmaps[i].addr, mmaps[i].block.size); > + free(mmaps); > + return NULL; > +} > + > +static int read_high_speed(int buf_fd, char *data, unsigned int block_size, > + struct mmap_block *mmaps, unsigned int mmaps_cnt) > +{ > + struct iio_buffer_block block; > + int ret; > + > + /** > + * This is where some buffer-pool management can do wonders, > + * but for the sake of this sample-code, we're just going to > + * copy the data and re-enqueue it back > + */ > + memset(&block, 0, sizeof(block)); > + ret = ioctl(buf_fd, IIO_BUFFER_BLOCK_DEQUEUE_IOCTL, &block); > + if (ret < 0) > + return ret; > + > + /* check for weird conditions */ > + if (block.bytes_used > block_size) { > + fprintf(stderr, > + "Got a bigger block (%u) than expected (%u)\n", > + block.bytes_used, block_size); > + return -EFBIG; > + } > + > + if (block.bytes_used < block_size) { > + /** > + * This can be normal, with some real-world data > + * terminating abruptly. But log it. > + */ > + fprintf(stderr, > + "Got a smaller block (%u) than expected (%u)\n", > + block.bytes_used, block_size); > + } > + > + /* memcpy() the data, we lose some more performance here :p */ > + memcpy(data, mmaps[block.id].addr, block.bytes_used); > + > + /* and re-queue this back */ > + ret = ioctl(buf_fd, IIO_BUFFER_BLOCK_ENQUEUE_IOCTL, &mmaps[block.id].block); > + if (ret < 0) > + return ret; > + > + return block.bytes_used; > +} > + forgot to remove this extra line; will make a note, for the next re-spin; after some feedback > + > static void print_usage(void) > { > fprintf(stderr, "Usage: generic_buffer [options]...\n" > @@ -249,6 +377,7 @@ static void print_usage(void) > " -c Do n conversions, or loop forever if n < 0\n" > " -e Disable wait for event (new data)\n" > " -g Use trigger-less mode\n" > + " -h Use high-speed buffer access\n" > " -l Set buffer length to n samples\n" > " --device-name -n \n" > " --device-num -N \n" > @@ -356,9 +485,15 @@ int main(int argc, char **argv) > > struct iio_channel_info *channels = NULL; > > + static bool use_high_speed = false; > + unsigned int block_size; > + int nblocks = 16; /* default */ > + int mmaps_cnt = 0; > + struct mmap_block *mmaps = NULL; > + > register_cleanup(); > > - while ((c = getopt_long(argc, argv, "aAb:c:egl:n:N:t:T:w:?", longopts, > + while ((c = getopt_long(argc, argv, "aAb:c:eghl:n:N:t:T:w:?", longopts, > NULL)) != -1) { > switch (c) { > case 'a': > @@ -396,6 +531,9 @@ int main(int argc, char **argv) > case 'g': > notrigger = 1; > break; > + case 'h': > + use_high_speed = true; > + break; > case 'l': > errno = 0; > buf_len = strtoul(optarg, &dummy, 10); > @@ -661,6 +799,29 @@ int main(int argc, char **argv) > goto error; > } > > + scan_size = size_from_channelarray(channels, num_channels); > + block_size = scan_size * buf_len; > + /** > + * Need to enable high-speed before configuring length/enable. > + * Otherwise, the DMA buffer will work in fileio mode, > + * and mmap won't work. > + */ > + if (use_high_speed) { > + /** > + * The block_size for one block is the same as 'data', but it > + * doesn't need to be the same size. It is easier for the sake > + * of this example. > + */ > + mmaps = enable_high_speed(buf_fd, block_size, nblocks); > + if (!mmaps) { > + fprintf(stderr, "Could not enable high-speed mode\n"); > + ret = -errno; > + goto error; > + } > + mmaps_cnt = nblocks; > + printf("Using high-speed mode\n"); > + } > + > /* Setup ring buffer parameters */ > ret = write_sysfs_int("length", buf_dir_name, buf_len); > if (ret < 0) > @@ -675,8 +836,7 @@ int main(int argc, char **argv) > goto error; > } > > - scan_size = size_from_channelarray(channels, num_channels); > - data = malloc(scan_size * buf_len); > + data = malloc(block_size); > if (!data) { > ret = -ENOMEM; > goto error; > @@ -719,7 +879,13 @@ int main(int argc, char **argv) > toread = 64; > } > > - read_size = read(buf_fd, data, toread * scan_size); > + if (use_high_speed) { > + read_size = read_high_speed(buf_fd, data, block_size, > + mmaps, mmaps_cnt); > + } else { > + read_size = read(buf_fd, data, toread * scan_size); > + } > + > if (read_size < 0) { > if (errno == EAGAIN) { > fprintf(stderr, "nothing available\n"); > @@ -738,8 +904,14 @@ int main(int argc, char **argv) > > if (fd >= 0 && close(fd) == -1) > perror("Failed to close character device"); > - if (buf_fd >= 0 && close(buf_fd) == -1) > - perror("Failed to close buffer"); > + for (i = 0; i < mmaps_cnt; i++) > + munmap(mmaps[i].addr, mmaps[i].block.size); > + free(mmaps); > + if (buf_fd >= 0) { > + ioctl(buf_fd, IIO_BUFFER_BLOCK_FREE_IOCTL, 0); > + if (close(buf_fd) == -1) > + perror("Failed to close buffer"); > + } > free(buffer_access); > free(data); > free(buf_dir_name); > -- > 2.17.1 >