Hi Yunhan,
On Fri, Sep 29, 2017 at 8:04 AM, Yunhan Wang <yunhanw@xxxxxxxxxxxx> wrote:
> Hi, Luiz
>
> May I ask several questions about acquire write implementation?
>
> On Wed, Sep 20, 2017 at 12:44 AM, Luiz Augusto von Dentz
> <luiz.dentz@xxxxxxxxx> wrote:
>> From: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
>>
>> This enables IO via file descriptors using AcquireWrite if server
>> implements it.
>> ---
>> src/gatt-database.c | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 142 insertions(+)
>>
>> diff --git a/src/gatt-database.c b/src/gatt-database.c
>> index 61eed71d6..239fe5384 100644
>> --- a/src/gatt-database.c
>> +++ b/src/gatt-database.c
>> @@ -33,6 +33,7 @@
>> #include "gdbus/gdbus.h"
>> #include "src/shared/util.h"
>> #include "src/shared/queue.h"
>> +#include "src/shared/io.h"
>> #include "src/shared/att.h"
>> #include "src/shared/gatt-db.h"
>> #include "src/shared/gatt-server.h"
>> @@ -117,6 +118,7 @@ struct external_chrc {
>> uint8_t props;
>> uint8_t ext_props;
>> uint32_t perm;
>> + struct io *write_io;
>> struct gatt_db_attribute *attrib;
>> struct gatt_db_attribute *ccc;
>> struct queue *pending_reads;
>> @@ -325,6 +327,8 @@ static void chrc_free(void *data)
>> {
>> struct external_chrc *chrc = data;
>>
>> + io_destroy(chrc->write_io);
>> +
>> queue_destroy(chrc->pending_reads, cancel_pending_read);
>> queue_destroy(chrc->pending_writes, cancel_pending_write);
>>
>> @@ -1789,6 +1793,128 @@ static struct pending_op *send_write(struct btd_device *device,
>> return NULL;
>> }
>>
>> +static bool pipe_hup(struct io *io, void *user_data)
>> +{
>> + struct external_chrc *chrc = user_data;
>> +
>> + DBG("%p closed\n", io);
>> +
>> + if (io == chrc->write_io)
>> + chrc->write_io = NULL;
>> +
>> + io_destroy(io);
>> +
>> + return false;
>> +}
>> +
>> +static struct io *pipe_io_new(int fd, void *user_data)
>> +{
>> + struct io *io;
>> +
>> + io = io_new(fd);
>> +
>> + io_set_close_on_destroy(io, true);
>> +
>> + io_set_disconnect_handler(io, pipe_hup, user_data, NULL);
>> +
>> + return io;
>> +}
>> +
>> +static int pipe_io_send(struct io *io, const void *data, size_t len)
>> +{
>> + struct iovec iov;
>> +
>> + iov.iov_base = (void *) data;
>> + iov.iov_len = len;
>> +
>> + return io_send(io, &iov, 1);
>> +}
>> +
>> +static void acquire_write_reply(DBusMessage *message, void *user_data)
>> +{
>> + struct pending_op *op = user_data;
>> + struct external_chrc *chrc;
>> + DBusError err;
>> + int fd;
>> + uint16_t mtu;
>> +
>> + chrc = gatt_db_attribute_get_user_data(op->attrib);
>> + dbus_error_init(&err);
>> +
>> + if (dbus_set_error_from_message(&err, message) == TRUE) {
>> + error("Failed to acquire write: %s\n", err.name);
>> + dbus_error_free(&err);
>> + goto retry;
>> + }
>> +
>> + if ((dbus_message_get_args(message, NULL, DBUS_TYPE_UNIX_FD, &fd,
>> + DBUS_TYPE_UINT16, &mtu,
>> + DBUS_TYPE_INVALID) == false)) {
>> + error("Invalid AcquireWrite response\n");
>> + goto retry;
>> + }
>> +
>> + DBG("AcquireWrite success: fd %d MTU %u\n", fd, mtu);
>> +
>> + chrc->write_io = pipe_io_new(fd, chrc);
>> +
>> + if (pipe_io_send(chrc->write_io, op->data.iov_base,
>> + op->data.iov_len) < 0)
>> + goto retry;
>> +
>> + return;
>> +
>> +retry:
>> + send_write(op->device, op->attrib, chrc->proxy, NULL, op->id,
>> + op->data.iov_base, op->data.iov_len, 0);
>> +}
>> +
>> +static void acquire_write_setup(DBusMessageIter *iter, void *user_data)
>> +{
>> + struct pending_op *op = user_data;
>> + DBusMessageIter dict;
>> + struct bt_gatt_server *server;
>> + uint16_t mtu;
>> +
>> + dbus_message_iter_open_container(iter, DBUS_TYPE_ARRAY,
>> + DBUS_DICT_ENTRY_BEGIN_CHAR_AS_STRING
>> + DBUS_TYPE_STRING_AS_STRING
>> + DBUS_TYPE_VARIANT_AS_STRING
>> + DBUS_DICT_ENTRY_END_CHAR_AS_STRING,
>> + &dict);
>> +
>> + append_options(&dict, op);
>> +
>> + server = btd_device_get_gatt_server(op->device);
>> +
>> + mtu = bt_gatt_server_get_mtu(server);
>> +
>> + dict_append_entry(&dict, "MTU", DBUS_TYPE_UINT16, &mtu);
>> +
>> + dbus_message_iter_close_container(iter, &dict);
>> +}
>> +
>> +static struct pending_op *acquire_write(struct external_chrc *chrc,
>> + struct btd_device *device,
>> + struct gatt_db_attribute *attrib,
>> + unsigned int id,
>> + const uint8_t *value, size_t len)
>> +{
>> + struct pending_op *op;
>> +
>> + op = pending_write_new(device, NULL, attrib, id, value, len, 0);
>> +
>> + if (g_dbus_proxy_method_call(chrc->proxy, "AcquireWrite",
>> + acquire_write_setup,
>> + acquire_write_reply,
>> + op, pending_op_free))
>> + return op;
>> +
>> + pending_op_free(op);
>> +
>> + return NULL;
>> +}
>> +
>> static uint8_t ccc_write_cb(uint16_t value, void *user_data)
>> {
>> struct external_chrc *chrc = user_data;
>> @@ -2090,6 +2216,7 @@ static void chrc_write_cb(struct gatt_db_attribute *attrib,
>> struct external_chrc *chrc = user_data;
>> struct btd_device *device;
>> struct queue *queue;
>> + DBusMessageIter iter;
>>
>> if (chrc->attrib != attrib) {
>> error("Write callback called with incorrect attribute");
>> @@ -2102,6 +2229,21 @@ static void chrc_write_cb(struct gatt_db_attribute *attrib,
>> goto fail;
>> }
>>
>> + if (chrc->write_io) {
>> + if (pipe_io_send(chrc->write_io, value, len) < 0) {
>> + error("Unable to write: %s", strerror(errno));
>> + goto fail;
>> + }
>> +
>> + gatt_db_attribute_write_result(attrib, id, 0);
>> + return;
>> + }
>> +
> Could you elaborate more about this part of codes, why are you using
> pipe_io_send to update value instead of dbus?
This is doing the write via fd if write_io has been acquired, the
whole point is avoiding D-Bus.
>> + if (g_dbus_proxy_get_property(chrc->proxy, "WriteAcquired", &iter)) {
>> + if (acquire_write(chrc, device, attrib, id, value, len))
>> + return;
>> + }
>> +
>
> Currently my expected scenario is to get MTU when first Gatt Write(
> write with response) comes in specific characteristic, for example, I
> use iphone as ble central and write value in Characteristic A on Bluez
> peripheral, Bluez peripheral get negotiated MTU when first write comes
> in. From this part of codes, it seems it return immediately after
> acquire_write is called, how can we move forward and write value to
> peripheral application? What is the design idea here?
After AcquireWrite the data is sent via fd as well:
https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/src/gatt-database.c#n1891
> The below is earlier draft idea for this MTU acquisition in server side.
> https://www.spinics.net/lists/linux-bluetooth/msg71961.html
>
>> if (!(chrc->props & BT_GATT_CHRC_PROP_WRITE_WITHOUT_RESP))
>> queue = chrc->pending_writes;
>> else
>> --
>> 2.13.5
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in
>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Luiz Augusto von Dentz
--
To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
