STRUCT DWC2_HOST_CHAN(9)

🎀 NAME 🎀

struct dwc2_host_chan — Software host channel descriptor 💅

okay bestie, welcome to the struct dwc2_host_chan(9) page from the Kernel API Manual. This is literally the software host channel descriptor — the struct that keeps a single host channel’s whole vibe together. 🫶

✨ SYNOPSIS ✨

struct dwc2_host_chan {
    u8 hc_num;
    unsigned dev_addr:7;
    unsigned ep_num:4;
    unsigned ep_is_in:1;
    unsigned speed:4;
    unsigned ep_type:2;
    unsigned max_packet:11;
    unsigned data_pid_start:2;
  #define DWC2_HC_PID_DATA0       TSIZ_SC_MC_PID_DATA0;
  #define DWC2_HC_PID_DATA2       TSIZ_SC_MC_PID_DATA2;
  #define DWC2_HC_PID_DATA1       TSIZ_SC_MC_PID_DATA1;
  #define DWC2_HC_PID_MDATA       TSIZ_SC_MC_PID_MDATA;
  #define DWC2_HC_PID_SETUP       TSIZ_SC_MC_PID_SETUP;
    unsigned multi_count:2;
    u8 *xfer_buf;
    dma_addr_t xfer_dma;
    dma_addr_t align_buf;
    u32 xfer_len;
    u32 xfer_count;
    u16 start_pkt_count;
    u8 xfer_started;
    u8 do_ping;
    u8 error_state;
    u8 halt_on_queue;
    u8 halt_pending;
    u8 do_split;
    u8 complete_split;
    u8 hub_addr;
    u8 hub_port;
    u8 xact_pos;
  #define DWC2_HCSPLT_XACTPOS_MID HCSPLT_XACTPOS_MID;
  #define DWC2_HCSPLT_XACTPOS_END HCSPLT_XACTPOS_END;
  #define DWC2_HCSPLT_XACTPOS_BEGIN HCSPLT_XACTPOS_BEGIN;
  #define DWC2_HCSPLT_XACTPOS_ALL HCSPLT_XACTPOS_ALL;
    u8 requests;
    u8 schinfo;
    u16 ntd;
    enum dwc2_halt_status halt_status;
    u32 hcint;
    struct dwc2_qh *qh;
    struct list_head hc_list_entry;
    dma_addr_t desc_list_addr;
    u32 desc_list_sz;
    struct list_head split_order_list_entry;
};

💖 Members 💖

Here’s the member-by-member breakdown, no skipping, periodt:

• hc_num — Host channel number, used for register address lookup. 🔎
• dev_addr — Address of the device.
• ep_num — Endpoint of the device.
• ep_is_in — Endpoint direction.
• speed — Device speed. One of the following values:
  • USB_SPEED_LOW
  • USB_SPEED_FULL
  • USB_SPEED_HIGH
• ep_type — Endpoint type. One of the following values:
  • USB_ENDPOINT_XFER_CONTROL: 0
  • USB_ENDPOINT_XFER_ISOC: 1
  • USB_ENDPOINT_XFER_BULK: 2
  • USB_ENDPOINT_XFER_INTR: 3
• max_packet — Max packet size in bytes.
• data_pid_start — PID for initial transaction. 0: DATA0, 1: DATA2, 2: DATA1, 3: MDATA (non-Control EP), SETUP (Control EP).
• multi_count — Number of additional periodic transactions per (micro)frame.
• xfer_buf — Pointer to current transfer buffer position.
• xfer_dma — DMA address of xfer_buf.
• align_buf — In Buffer DMA mode this will be used if xfer_buf is not DWORD aligned.
• xfer_len — Total number of bytes to transfer.
• xfer_count — Number of bytes transferred so far.
• start_pkt_count — Packet count at start of transfer.
• xfer_started — True if the transfer has been started.
• do_ping — True if a PING request should be issued on this channel.
• error_state — True if the error count for this transaction is non-zero.
• halt_on_queue — True if this channel should be halted the next time a request is queued for the channel. This is necessary in slave mode if no request queue space is available when an attempt is made to halt the channel.
• halt_pending — True if the host channel has been halted, but the core is not finished flushing queued requests.
• do_split — Enable split for the channel.
• complete_split — Enable complete split.
• hub_addr — Address of high speed hub for the split.
• hub_port — Port of the low/full speed device for the split.
• xact_pos — Split transaction position. One of the following values:
  • DWC2_HCSPLT_XACTPOS_MID
  • DWC2_HCSPLT_XACTPOS_BEGIN
  • DWC2_HCSPLT_XACTPOS_END
  • DWC2_HCSPLT_XACTPOS_ALL
• requests — Number of requests issued for this channel since it was assigned to the current transfer (not counting PINGs).
• schinfo — Scheduling micro-frame bitmap.
• ntd — Number of transfer descriptors for the transfer.
• halt_status — Reason for halting the host channel.
• hcint — Contents of the HCINT register when the interrupt came.
• qh — QH for the transfer being processed by this channel.
• hc_list_entry — For linking to list of host channels.
• desc_list_addr — Current QH’s descriptor list DMA address.
• desc_list_sz — Current QH’s descriptor list size.
• split_order_list_entry — List entry for keeping track of the order of splits.

🌈 Description 🌈

This structure represents the state of a single host channel when acting in host mode. It contains the data items needed to transfer packets to an endpoint via a host channel. Iconic little state blob, honestly. ✨

🦋 SEE ALSO 🦋

• Kernel file ./drivers/usb/dwc2/hcd.h
• struct dwc2_tt(9)
• struct dwc2_hs_transfer_time(9)
• struct dwc2_qh(9)
• struct dwc2_qtd(9)
• dwc2_handle_hcd_intr(9)
• dwc2_hcd_stop(9)
• dwc2_hcd_is_b_host(9)
• dwc2_hcd_dump_state(9)

k bye bestie — this page comes from ./drivers/usb/dwc2, dated October 2026, and it’s the struct dwc2_host_chan(9) manual. slay and read the source 💖✨