[jira] [Created] (MYNEWT-291) BLE Host - Split GATT attribute access function into more specific events

["Christopher Collins (JIRA)" <ji...@apache.org>]

Christopher Collins created MYNEWT-291:
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             Summary: BLE Host - Split GATT attribute access function into more specific events
                 Key: MYNEWT-291
                 URL: https://issues.apache.org/jira/browse/MYNEWT-291
             Project: Mynewt
          Issue Type: Bug
          Components: Nimble
            Reporter: Christopher Collins
            Assignee: Christopher Collins
             Fix For: 0.9.0


Nimble notifies the app that a characteristic or descriptor is being accessed via an access callback.  The access callback takes a context parameter which points to an instance of the following union:

{noformat}
union ble_gatt_access_ctxt {
    struct {
        const struct ble_gatt_chr_def *chr;
        void *data;
        int len;
    } chr_access;

    struct {
        const struct ble_gatt_dsc_def *dsc;
        void *data;
        int len;
    } dsc_access;
};
{noformat}

This is problematic because the user may wish to point the _data_ fields to read-only data, requiring them to "cast away const."  This looks questionable in code, and is difficult to document in the user guide with a straight face.

Instead, we should change the union to the following:
union ble_gatt_access_ctxt {
    struct {
        const struct ble_gatt_chr_def *chr;
        const void *data;
        int len;
    } chr_read;

    struct {
        const struct ble_gatt_chr_def *chr;
        void *data;
        int len;
    } chr_write;

    struct {
        const struct ble_gatt_dsc_def *dsc;
        const void *data;
        int len;
    } dsc_read;

    struct {
        const struct ble_gatt_dsc_def *dsc;
        void *data;
        int len;
    } dsc_write;
};



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