ssi.h (4014B)
1 /* QEMU Synchronous Serial Interface support. */ 2 3 /* 4 * In principle SSI is a point-point interface. As such the qemu 5 * implementation has a single peripheral on a "bus". 6 * However it is fairly common for boards to have multiple peripherals 7 * connected to a single master, and select devices with an external 8 * chip select. This is implemented in qemu by having an explicit mux device. 9 * It is assumed that master and peripheral are both using the same transfer 10 * width. 11 */ 12 13 #ifndef QEMU_SSI_H 14 #define QEMU_SSI_H 15 16 #include "hw/qdev-core.h" 17 #include "qom/object.h" 18 19 typedef enum SSICSMode SSICSMode; 20 21 #define TYPE_SSI_PERIPHERAL "ssi-peripheral" 22 OBJECT_DECLARE_TYPE(SSIPeripheral, SSIPeripheralClass, 23 SSI_PERIPHERAL) 24 25 #define SSI_GPIO_CS "ssi-gpio-cs" 26 27 enum SSICSMode { 28 SSI_CS_NONE = 0, 29 SSI_CS_LOW, 30 SSI_CS_HIGH, 31 }; 32 33 /* Peripherals. */ 34 struct SSIPeripheralClass { 35 DeviceClass parent_class; 36 37 void (*realize)(SSIPeripheral *dev, Error **errp); 38 39 /* if you have standard or no CS behaviour, just override transfer. 40 * This is called when the device cs is active (true by default). 41 */ 42 uint32_t (*transfer)(SSIPeripheral *dev, uint32_t val); 43 /* called when the CS line changes. Optional, devices only need to implement 44 * this if they have side effects associated with the cs line (beyond 45 * tristating the txrx lines). 46 */ 47 int (*set_cs)(SSIPeripheral *dev, bool select); 48 /* define whether or not CS exists and is active low/high */ 49 SSICSMode cs_polarity; 50 51 /* if you have non-standard CS behaviour override this to take control 52 * of the CS behaviour at the device level. transfer, set_cs, and 53 * cs_polarity are unused if this is overwritten. Transfer_raw will 54 * always be called for the device for every txrx access to the parent bus 55 */ 56 uint32_t (*transfer_raw)(SSIPeripheral *dev, uint32_t val); 57 }; 58 59 struct SSIPeripheral { 60 DeviceState parent_obj; 61 62 /* cache the class */ 63 SSIPeripheralClass *spc; 64 65 /* Chip select state */ 66 bool cs; 67 }; 68 69 extern const VMStateDescription vmstate_ssi_peripheral; 70 71 #define VMSTATE_SSI_PERIPHERAL(_field, _state) { \ 72 .name = (stringify(_field)), \ 73 .size = sizeof(SSIPeripheral), \ 74 .vmsd = &vmstate_ssi_peripheral, \ 75 .flags = VMS_STRUCT, \ 76 .offset = vmstate_offset_value(_state, _field, SSIPeripheral), \ 77 } 78 79 DeviceState *ssi_create_peripheral(SSIBus *bus, const char *name); 80 /** 81 * ssi_realize_and_unref: realize and unref an SSI peripheral 82 * @dev: SSI peripheral to realize 83 * @bus: SSI bus to put it on 84 * @errp: error pointer 85 * 86 * Call 'realize' on @dev, put it on the specified @bus, and drop the 87 * reference to it. Errors are reported via @errp and by returning 88 * false. 89 * 90 * This function is useful if you have created @dev via qdev_new() 91 * (which takes a reference to the device it returns to you), so that 92 * you can set properties on it before realizing it. If you don't need 93 * to set properties then ssi_create_peripheral() is probably better (as it 94 * does the create, init and realize in one step). 95 * 96 * If you are embedding the SSI peripheral into another QOM device and 97 * initialized it via some variant on object_initialize_child() then 98 * do not use this function, because that family of functions arrange 99 * for the only reference to the child device to be held by the parent 100 * via the child<> property, and so the reference-count-drop done here 101 * would be incorrect. (Instead you would want ssi_realize(), which 102 * doesn't currently exist but would be trivial to create if we had 103 * any code that wanted it.) 104 */ 105 bool ssi_realize_and_unref(DeviceState *dev, SSIBus *bus, Error **errp); 106 107 /* Master interface. */ 108 SSIBus *ssi_create_bus(DeviceState *parent, const char *name); 109 110 uint32_t ssi_transfer(SSIBus *bus, uint32_t val); 111 112 #endif