• Christophe Ricard's avatar
    NFC: ST21NFCA: Add driver for STMicroelectronics ST21NFCA NFC Chip · 68957303
    Christophe Ricard authored
    Add driver for STMicroelectronics ST21NFCA NFC controller.
    ST21NFCA is using HCI protocol, shdlc as LLC layer & I2C as
    communication protocol.
    
    Adding support for Reader/Writer mode with Tag type 1/2/3/4 A & B.
    It is using proprietary gate 15 for ISO14443-3 such as type 1 &
    type 2 tags. It is using proprietary gate 14 for type F tags.
    ST21NFCA_DEVICE_MGNT_GATE gives access to proprietary CLF configuration.
    Standard gate for ISO14443-4 A (13) & B (11) are also used.
    
    ST21NFCA specific mecanism:
    
    One particular point to notice for the data handling is that frame
    does not contain any length value. Therefore the i2c part of this driver
    is managing the reception with a read length sequence until the end of
    frame (0x7e) is reached.
    
    In order to avoid conflict between sof & eof a mecanism
    called byte stuffing concist of an escape byte (0x7d) insertion before
    special byte (0x7e, 0x7d). The special byte is then xored with 0x20.
    
    In this driver, When data are available in the CLF, the interrupt
    gpio is driven to active state and triggered an interrupt.
    Once the i2c_master_recv start, the interrupt gpio is driven to idle
    state until its complete. If the frame is incomplete or data are still
    available, interrupts will be triggered again.
    Signed-off-by: default avatarChristophe Ricard <christophe-h.ricard@st.com>
    Signed-off-by: default avatarSamuel Ortiz <sameo@linux.intel.com>
    68957303
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