STRUCT PXA_EP(9)

💜 struct pxa_ep(9) — the pxa endpoint, bestie edition 🎀

okay so this is a page from the Kernel API Manual about struct pxa_ep, and honestly? it's giving "old USB gadget driver lore" and i'm obsessed. let's get into it 💅

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✨ SYNOPSIS ✨

here's the whole struct, laid out exactly as it is, no cap:

struct pxa_ep {
    struct pxa_udc          *dev;
    struct list_head        queue;
    spinlock_t lock;
    unsigned enabled:1;
    unsigned in_handle_ep:1;
    unsigned idx:5;
    char *name;
    unsigned dir_in:1;
    unsigned addr:4;
    unsigned config:2;
    unsigned interface:3;
    unsigned alternate:3;
    unsigned fifo_size;
    unsigned type;
  #ifdef CONFIG_PM;
    u32 udccsr_value;
    u32 udccr_value;
  #endif;
    struct stats            stats;
 };

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🦋 Members 🦋

bestie, meet the fields. every single one. line by line, no skipping 🙈

• dev — the udc device 💖
• queue — the requests queue 🎀
• lock — the lock that guards the pxa_ep data (that means the queues and the stats) 🔒
• enabled — true when the endpoint is enabled — and to be clear, that means not stopped by the gadget layer ✨
• in_handle_ep — the number of recursions of the handle_ep function. it exists to prevent deadlocks or infinite recursions of types:

irq->handle_ep->req_done->req.complete->pxa_ep_queue->handle_ep

or

pxa_ep_queue->handle_ep->req_done->req.complete->pxa_ep_queue

like, that's the whole reason. protecting us from ourselves 😭

• idx — the endpoint index (1 => epA, 2 => epB, ..., 24 => epX) 🔢
• name — the endpoint name (for trace/debug purpose) 🏷️
• dir_in — 1 if it's an IN endpoint, 0 if it's an OUT endpoint 🌈
• addr — the usb endpoint number 📮
• config — the configuration in which this endpoint is active ⚙️
• interface — the interface in which this endpoint is active 🔌
• alternate — the altsetting in which this endpoint is active 🌀
• fifo_size — max packet size in the endpoint fifo 📦
• type — the endpoint type (bulk, iso, int, ...) 👑
• udccsr_value — save register of UDCCSR0 for suspend/resume 💾
• udccr_value — save register of UDCCR for suspend/resume 💾
• stats — endpoint statistics 📊

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💀 Description 💀

okay so this is where it gets real. the *PROBLEM* is that pxa's endpoint configuration scheme is both misdesigned and full of implementation bugs. misdesigned how? it cares about config/interface/altsetting, which places needless limits on device capability. and the bugs? they force it to be set up for use more or less like a pxa255. yeah. that's the situation. 🙃

and because we define the pxa_ep statically, we must guess all needed pxa_ep for all gadget which may work with this udc driver. guessing. statically. iconic in the worst way ngl 😭

fr fr, that's the actual documented state of things — i'm not adding drama, the manpage said *PROBLEM* with the asterisks and everything 💀

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🌸 SEE ALSO 🌸

go read these too, bestie, they're in the kernel file ./drivers/usb/gadget/udc/pxa27x_udc.h 👀

• struct udc_usb_ep(9)
• struct pxa27x_request(9)
• struct pxa_udc(9)

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and that's the whole vibe check 🫶 this page lives in ./drivers/usb/gadget/udc and it's dated October 2026 — shoutout to the source, mwah 💋✨🎀