2019-04-15 23:56:01 -03:00
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2012-05-14 15:51:52 +02:00
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2024-01-30 13:23:40 +01:00
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2012-05-14 15:51:52 +02:00
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2024-08-10 20:00:05 -04:00
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2012-05-14 15:51:52 +02:00
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2019-04-15 23:56:01 -03:00
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2012-05-14 15:51:52 +02:00
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2019-04-15 23:56:01 -03:00
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2012-05-14 15:51:52 +02:00
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2022-11-18 15:14:22 -08:00
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2012-05-14 15:51:52 +02:00
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2024-01-30 13:23:40 +01:00
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usb: gadget: f_fs: Add zero-length packet ioctl
When transferring data from a USB gadget to a host, a transfer is
considered complete when the host receives a short packet (a packet
smaller than wMaxPacketSize). If the total transfer length is an
exact multiple of wMaxPacketSize, a Zero-Length Packet (ZLP) must
be appended to signal the end of the transfer.
FunctionFS currently provides no mechanism for userspace to instruct
the kernel to set the `req->zero` flag on transfers. Userspace
workarounds, such as manually submitting separate 0-byte requests,
may not be available for legacy protocols which must maintain write
behavior compatibility when moved to functionfs implementations.
To resolve this, introduce a new ioctl, FUNCTIONFS_ENDPOINT_ENABLE_ZLP,
which takes a pointer to a __u32 flag. When enabled, all subsequent
transfers on that endpoint will have the `req->zero` flag set, allowing
the underlying USB Device Controller (UDC) hardware to automatically
append a ZLP only when mathematically required. For logical transfers
chunked across multiple requests, userspace can dynamically toggle this
flag, enabling it only prior to submitting the final chunk.
The flag defaults to false to maintain backward compatibility. Once
enabled, the state is persistent for the lifetime of the endpoint and
will not be reset by opening or closing the endpoint file descriptors.
Assisted-by: Gemini-CLI:gemini-3.1-pro-preview
Signed-off-by: Neill Kapron <nkapron@google.com>
Link: https://patch.msgid.link/20260619040609.4010746-4-nkapron@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-06-19 04:06:05 +00:00
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usb: gadget: f_fs: Introduce rw_proxy file descriptors
Currently, FunctionFS exposes each USB endpoint as a separate,
unidirectional file descriptor (e.g., `ep1` for IN, `ep2` for OUT).
While this mirrors the underlying hardware structure, it forces
userspace daemons implementing bidirectional protocols to manage
multiple file descriptors. When dealing with legacy protocols which
require exposing a single, bi-directional fd to userspace, this becomes
problematic.
This patch introduces the `FUNCTIONFS_RW_PROXY_EPS` UAPI flag. When
passed in the descriptor header during initialization, FunctionFS
provisions a "rw_proxy" bidirectional file descriptor (e.g., `ep1_rw`)
alongside every pair of IN/OUT endpoints.
Implementation details:
- RW proxy files act as a pure VFS alias, proxying operations
directly to the base ffs_epfile instances. A `read()` proxies to
the OUT endpoint's file, and a `write()` proxies to the IN file.
- Because operations are proxied natively, they reuse the underlying
base endpoint's lock (`epfile->mutex`) and tracking state. This
serializes concurrent I/O, preventing buffer corruption or races
even if userspace mixes transfers across both the rw_proxy and base files
while allowing full-duplex synchronous operations to occur concurrently
without serializing on a single lock.
- Control operations (like IOCTLs) and intentional stalls (via
reverse-direction I/O) must still be issued on the base endpoints, as the
rw_proxy returns `-ENOTTY` for IOCTLs and cannot trigger stalls.
Assisted-by: Antigravity:gemini-3.1-pro
Signed-off-by: Neill Kapron <nkapron@google.com>
Link: https://patch.msgid.link/20260619040609.4010746-5-nkapron@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-06-19 04:06:06 +00:00
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2024-01-30 13:23:40 +01:00
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usb: gadget: f_fs: Introduce rw_proxy file descriptors
Currently, FunctionFS exposes each USB endpoint as a separate,
unidirectional file descriptor (e.g., `ep1` for IN, `ep2` for OUT).
While this mirrors the underlying hardware structure, it forces
userspace daemons implementing bidirectional protocols to manage
multiple file descriptors. When dealing with legacy protocols which
require exposing a single, bi-directional fd to userspace, this becomes
problematic.
This patch introduces the `FUNCTIONFS_RW_PROXY_EPS` UAPI flag. When
passed in the descriptor header during initialization, FunctionFS
provisions a "rw_proxy" bidirectional file descriptor (e.g., `ep1_rw`)
alongside every pair of IN/OUT endpoints.
Implementation details:
- RW proxy files act as a pure VFS alias, proxying operations
directly to the base ffs_epfile instances. A `read()` proxies to
the OUT endpoint's file, and a `write()` proxies to the IN file.
- Because operations are proxied natively, they reuse the underlying
base endpoint's lock (`epfile->mutex`) and tracking state. This
serializes concurrent I/O, preventing buffer corruption or races
even if userspace mixes transfers across both the rw_proxy and base files
while allowing full-duplex synchronous operations to occur concurrently
without serializing on a single lock.
- Control operations (like IOCTLs) and intentional stalls (via
reverse-direction I/O) must still be issued on the base endpoints, as the
rw_proxy returns `-ENOTTY` for IOCTLs and cannot trigger stalls.
Assisted-by: Antigravity:gemini-3.1-pro
Signed-off-by: Neill Kapron <nkapron@google.com>
Link: https://patch.msgid.link/20260619040609.4010746-5-nkapron@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-06-19 04:06:06 +00:00
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2024-01-30 13:23:40 +01:00
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